Connected mode mobility in new radio

ABSTRACT

The present application is at least directed to an apparatus in a network including a non-transitory memory including instructions stored thereon for obtaining a resource for accessing a target cell in the network. The apparatus includes a processor, operably coupled to the non-transitory memory, configured to execute the instructions of detecting plural beams associated with the target cell. The processor also executes the instructions of determining one or more of the plural detected beams meeting a threshold for performing random access. The processor also executes the instructions of evaluating if a physical random access channel (PRACH) resource is associated with the one or more determined beams meeting the threshold. The processor further executes the instructions of selecting one of the evaluated beams exhibiting a reference signal received power (RSRP) above a predetermined value. The processor even further executes the instructions of picking the PRACH resource associated with the selected beam.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage Application of InternationalPatent Application No. PCT/US2018/046050, filed Aug. 9, 2018, whichclaims the benefit of priority of U.S. Provisional application No.62/543,599 filed Aug. 10, 2017 entitled, “Connected Mode Mobility in NewRadio,” U.S. Provisional application No. 62/564,452 filed Sep. 28, 2017,entitled, “Connected Mode Mobility in New Radio,” and U.S. Provisionalapplication No. 62/580,639 filed Nov. 2, 2017, entitled, “Connected ModeMobility in New Radio,” the contents of which are incorporated byreference in their entireties.

FIELD

The present application is directed to methods and systems for connectedmode mobility in new radio (NR).

BACKGROUND

RAN2 has agreed that the handover command may include a set of dedicatedand/or common PRACH resources that are associated with beams of thetarget cell. The dedicated PRACH resources, if provided, will beassociated with beams considered to be suitable, based on RRMmeasurements reported by the UE. However, given the propagationcharacteristics of the channel for high frequency deployments, it ispossible that the quality of one or more of beams that were consideredsuitable at the time of the measurement report has degraded by the timethe handover command is received.

In the scenario when UEs only consider beams associated with dedicatedPRACH resources when selecting the beam to access the target cell, theUE may select a lower quality beam requiring preamble retransmission(s)before successfully completing the random access procedure. Selecting abeam associated with a common PRACH resource and performing ContentionBased Random Access (CBRA) may be better than selecting a beamassociated with a dedicated PRACH resource and performing ContentionFree Random Access (CFRA).

Alternatively, if the UE selected the “best” beam from the superset ofbeams associated with dedicated and common PRACH resources, the UE mayselect a beam associated with a common PRACH resource that requires CBRAand may require preamble retransmission(s) due to collisions. In such ascenario, selecting a lower quality beam associated with a dedicatedPRACH resource and performing CFRA may be better.

For high frequency deployments, beamforming will be used to compensatefor high propagation loss. Several narrow high gain beams are expectedto be used to provide reliable coverage within a cell. Some beams willhave a higher concentration of UEs within their coverage than otherbeams. Attempting to access the target cell via a congested beam couldresult in increased interruption time during handover due to preamblecollisions, reception of back off indications, etc. Furthermore, evenwhen the UE is able to access the target cell via a congested beam, oncethe access is complete the UE may be required to switch to a differentbeam before commencing with data transmissions, which will furtherincrease the interruption time.

In long-term evolution (LTE) technology, UEs perform a random accessprocedure with the same set of configured parameters agnostic of theaccess request's purpose. However, a need exists in NR to support a morediverse set of use cases exhibiting different performance objectiveswhen performing an access request. A need also exists in the art tosupport a prioritized random access procedure for NR.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to limit the scope of theclaimed subject matter. The foregoing needs are met, to a great extent,by the present application describing.

One aspect of the present application is directed to an apparatus in anetwork including a non-transitory memory including instructions storedthereon for obtaining a resource for accessing a target cell in thenetwork. The apparatus includes a processor, operably coupled to thenon-transitory memory, configured to execute the instructions ofdetecting plural beams associated with the target cell. The processoralso executes the instructions of determining one or more of the pluraldetected beams meeting a threshold for performing random access. Theprocessor also executes the instructions of evaluating if a physicalrandom access channel (PRACH) resource is associated with the one ormore determined beams meeting the threshold. The processor furtherexecutes the instructions of selecting one of the evaluated beamsexhibiting a reference signal received power (RSRP) above apredetermined value. The processor even further executes theinstructions of picking the PRACH resource associated with the selectedbeam.

Another aspect of the application is directed to an apparatus in anetwork including a non-transitory memory including instructions storedthereon for physical random access channel (PRACH) resource selection.The apparatus includes a processor, operably coupled to thenon-transitory memory, configured to execute the instructions ofdetermining a list of contention free random access (RA) resources hasbeen received from a radio resource control (RRC). The processor alsoexecutes the instructions of determining if the list includes a group ofsynchronization signal block (SSB) indices or channel state informationreference signal (CSI-RS) indices. The processor also executes theinstructions of selecting an index from either the group of SSB indicesor CSI-RS indices. The processor further executes the instruction ofconfiguring a preamble index to a random access (RA) preamble indexassociated with the selected index. The processor even further executesthe instructions of transmitting the RA preamble corresponding to theindex to a cell in the network.

Yet another aspect of the application is directed to an apparatus in anetwork including a non-transitory memory including instructions storedthereon for performing handover to a target cell in the network. Theapparatus includes a processor, operably coupled to the non-transitorymemory, configured to execute the instructions of sending a measurementreport to a source node. The processor also executes the instructions ofreceiving, from the source node, a handover command message. Thehandover command message is based on the source node determining, basedupon the measurement report and radio resource monitoring (RRM)information, whether to assign the apparatus to the target cell. Thehandover command message is also based on the source node transmitting ahandover request to the target cell. The handover command message isfurther based on source node receiving a handover acknowledgementmessage from the target cell. The processor of the apparatus furtherexecutes the instructions of sending, based on the handover commandmessage, a random access preamble (RAP) to the target cell on a firstbeam. The processor of the apparatus even further executes theinstructions of receiving a random access response (RAR) from the targetcell.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof may be betterunderstood, and in order that the present contribution to the art may bebetter appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a more robust understanding of the application,reference is now made to the accompanying drawings, in which likeelements are referenced with like numerals. These drawings should not beconstrued to limit the application and are intended only to beillustrative.

FIG. 1A illustrates an exemplary communications system according to anembodiment.

FIG. 1B illustrates an exemplary apparatus configured for wirelesscommunication according to an embodiment.

FIG. 1C illustrates a system diagram of a radio access network and acore network according to an embodiment.

FIG. 1D illustrates a system diagram of a radio access network and acore network according to another embodiment.

FIG. 1E illustrates a system diagram of a radio access network and acore network according to yet another embodiment.

FIG. 1F illustrates a block diagram of an exemplary computing system incommunication with one or more networks previously shown in FIGS. 1A,1C, 1D and 1E according to an embodiment.

FIG. 2 illustrates a contention based random access procedure.

FIG. 3 illustrates cell coverage with sector beams and multiple highgain narrow beams.

FIG. 4 illustrates an embodiment of system information provisioning inNR.

FIG. 5 illustrates UE state machine and state transitions in NR.

FIG. 6 illustrates UE state machine and state transitions between NR/NGCand E-UTRAN/EPC.

FIG. 7 illustrates Intra-AMF/UPF Handover.

FIG. 8 illustrates a PRACH resource selection model.

FIG. 9 illustrates a PRACH resource selection model integration with aRRM measurement model according to an embodiment.

FIG. 10A illustrates a PRACH resource selection model integration with aRRM measurement model according to another embodiment.

FIG. 10B illustrates a PRACH resource selection model integration with aRRM measurement model according to yet another embodiment.

FIG. 11 illustrates a PRACH resource selection procedure according to anembodiment.

FIG. 12 illustrates a PRACH resource selection procedure according toanother embodiment.

FIG. 13 illustrates a PRACH resource selection procedure according toyet another embodiment.

FIG. 14 illustrates a PRACH resource selection procedure according toyet even another embodiment.

FIG. 15 illustrates an exemplary NR deployment scenario according toanother embodiment.

FIG. 16A illustrates a PRACH resource selection procedure according to afurther embodiment.

FIG. 16B illustrates a PRACH resource selection procedure according toyet a further embodiment.

FIG. 16C illustrates a PRACH resource selection procedure according toyet even a further embodiment.

FIG. 17 illustrates a load balancing between beams of a target cellduring random access according to another embodiment.

FIG. 18 illustrates a RAR used to direct UE to a different beamaccording to an embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

A detailed description of the illustrative embodiment will be discussedin reference to various figures, embodiments and aspects herein.Although this description provides detailed examples of possibleimplementations, it should be understood that the details are intendedto be examples and thus do not limit the scope of the application.

Reference in this specification to “one embodiment,” “an embodiment,”“one or more embodiments,” “an aspect” or the like means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment of thedisclosure. Moreover, the term “embodiment” in various places in thespecification is not necessarily referring to the same embodiment. Thatis, various features are described which may be exhibited by someembodiments and not by the other.

Generally, the application describes methods and systems for selectingthe beams to be included in the measurement report. One aspect of theapplication describes methods to optimally select the PRACH resourceused for accessing the target cell from the set of dedicated and/orcommon PRACH resources in the handover command. AnNR-RACH-ConfigDedicated IE may be used to signal the dedicated RACHconfiguration in the handover command. A PRACH resource selection modelmay be integrated with the RRM measurement model.

Another aspect of the application describes a method to perform PRACHresource selection from a set of PRACH resources associated with anarrow beam that may be used for a first access attempt. This may befollowed by PRACH resource selection from a set of PRACH resourceassociated with a wide beam that may be used for a second access attemptin the event the first access attempt is not successful.

A further aspect of the application describes a procedure that may beused to perform load balancing between the beams of the target cell whenperforming random access. A MAC RAR may optionally include a Beam SwitchCommand that may be used to direct the UE to use a different beam.

Yet a further aspect of the application is directed to prioritizedrandom access. This may include a method to assign priorities todifferent types of random access events. This may also include a methodto assign different sets of values to the random access parameters wherethe set of assigned values are based on the random access priority.

Definitions/Acronyms

Provided below are definitions for terms and phrases commonly used inthis application in Table 1.

TABLE 1 Acronym Term or Phrase AMF Access and Mobility Management ARQAutomatic Repeat Request AS Access Stratum CA Carrier Aggregation CBRAContention Based Random Access CFRA Contention Free Random Access CMASCommercial Mobile Alert System CN Core Network C-RNTI Cell Radio-NetworkTemporary Identifier CSI-RS Channel State Information Reference SignalDC Duel Connectivity DL Downlink DL-SCH Downlink Shared Channel DRXDiscontinuous Reception EAB Extended Access Barring eMBB Enhanced MobileBroadband eNB Evolved Node B EPC Evolved Packet Core ETWS Earthquake andTsunami Warning System E-UTRA Evolved Universal Terrestrial Radio AccessE-UTRAN Evolved Universal Terrestrial Radio Access Network FDD FrequencyDivision Duplex FFS For Further Study GERAN GSM EDGE Radio AccessNetwork gNB NR Node B GSM Global System for Mobile Communications HARQHybrid Automatic Repeat Request HNB Home eNB HO Handover IE InformationElement KPI Key Performance Indicators L1 Layer 1 L2 Layer 2 L3 Layer 3LTE Long Term Evolution MAC Medium Access Control MBMS MultimediaBroadcast Multicast Service MCG Master Cell Group NGC Next GenerationCore MIB Master Information Block MTC Machine-Type Communications mMTCMassive Machine Type Communication NAS Non-Access Stratum NR New RadioOFDM Orthogonal Frequency Division Multiplexing PCell Primary Cell PHYPhysical Layer PRACH Physical Random Access Channel QoS Quality ofService RACH Random Access Channel RAN Radio Access Network RAP RandomAccess Preamble RAR Random Access Response RAT Radio Access TechnologyRRC Radio Resource Control RRM Radio Resource Monitoring RSRP ReferenceSignal Received Power RSRQ Reference Signal Received Quality SAI ServiceArea Identities sCell Secondary Cell SCG Secondary Cell Group SC-PTMSingle Cell Point to Multipoint SDU Service Data Unit SI SystemInformation SIB System Information Block SN Sequence Number SRScheduling Request SS Synchronization Signal SSB SS Block sTAG SecondaryTime Advance Group TDD Time Divisional Duplex T/F Time/Frequency TRPTransmission and Reception Point TTI Transmission Time Interval UE UserEquipment UL Uplink UL-SCH Uplink Shared Channel UPF User Plane FunctionURLLC Ultra-Reliable and Low Latency Communications UTC CoordinatedUniversal TimeGeneral Architecture

The 3rd Generation Partnership Project (3GPP) develops technicalstandards for cellular telecommunications network technologies,including radio access, the core transport network, and servicecapabilities—including work on codecs, security, and quality of service.Recent radio access technology (RAT) standards include WCDMA (commonlyreferred as 3G), LTE (commonly referred as 4G), and LTE-Advancedstandards. 3GPP has begun working on the standardization of nextgeneration cellular technology, called New Radio (NR), which is alsoreferred to as “5G”. 3GPP NR standards development is expected toinclude the definition of next generation radio access technology (newRAT), which is expected to include the provision of new flexible radioaccess below 6 GHz, and the provision of new ultra-mobile broadbandradio access above 6 GHz. The flexible radio access is expected toconsist of a new, non-backwards compatible radio access in new spectrumbelow 6 GHz, and it is expected to include different operating modesthat can be multiplexed together in the same spectrum to address a broadset of 3GPP NR use cases with diverging requirements. The ultra-mobilebroadband is expected to include cmWave and mmWave spectrum that willprovide the opportunity for ultra-mobile broadband access for, e.g.,indoor applications and hotspots. In particular, the ultra-mobilebroadband is expected to share a common design framework with theflexible radio access below 6 GHz, with cmWave and mmWave specificdesign optimizations.

3GPP has identified a variety of use cases that NR is expected tosupport, resulting in a wide variety of user experience requirements fordata rate, latency, and mobility. The use cases include the followinggeneral categories: enhanced mobile broadband (e.g., broadband access indense areas, indoor ultra-high broadband access, broadband access in acrowd, 50+ Mbps everywhere, ultra-low cost broadband access, mobilebroadband in vehicles), critical communications, massive machine typecommunications, network operation (e.g., network slicing, routing,migration and interworking, energy savings), and enhancedvehicle-to-everything (eV2X) communications. Specific service andapplications in these categories include, e.g., monitoring and sensornetworks, device remote controlling, bi-directional remote controlling,personal cloud computing, video streaming, wireless cloud-based office,first responder connectivity, automotive ecall, disaster alerts,real-time gaming, multi-person video calls, autonomous driving,augmented reality, tactile internet, and virtual reality to name a few.All of these use cases and others are contemplated herein.

FIG. 1A illustrates one embodiment of an example communications system100 in which the methods and apparatuses described and claimed hereinmay be embodied. As shown, the example communications system 100 mayinclude wireless transmit/receive units (WTRUs) 102 a, 102 b, 102 c,and/or 102 d (which generally or collectively may be referred to as WTRU102), a radio access network (RAN) 103/104/105/103 b/104 b/105 b, a corenetwork 106/107/109, a public switched telephone network (PSTN) 108, theInternet 110, and other networks 112, though it will be appreciated thatthe disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d, 102 e may be any type of apparatus or deviceconfigured to operate and/or communicate in a wireless environment.Although each WTRU 102 a, 102 b, 102 c, 102 d, 102 e is depicted inFIGS. 1A-1E as a hand-held wireless communications apparatus, it isunderstood that with the wide variety of use cases contemplated for 5Gwireless communications, each WTRU may comprise or be embodied in anytype of apparatus or device configured to transmit and/or receivewireless signals, including, by way of example only, user equipment(UE), a mobile station, a fixed or mobile subscriber unit, a pager, acellular telephone, a personal digital assistant (PDA), a smartphone, alaptop, a tablet, a netbook, a notebook computer, a personal computer, awireless sensor, consumer electronics, a wearable device such as a smartwatch or smart clothing, a medical or eHealth device, a robot,industrial equipment, a drone, a vehicle such as a car, truck, train, orairplane, and the like.

The communications system 100 may also include a base station 114 a anda base station 114 b. Base stations 114 a may be any type of deviceconfigured to wirelessly interface with at least one of the WTRUs 102 a,102 b, 102 c to facilitate access to one or more communication networks,such as the core network 106/107/109, the Internet 110, and/or the othernetworks 112. Base stations 114 b may be any type of device configuredto wiredly and/or wirelessly interface with at least one of the RRHs(Remote Radio Heads) 118 a, 118 b and/or TRPs (Transmission andReception Points) 119 a, 119 b to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the other networks 112. RRHs 118 a, 118 b may beany type of device configured to wirelessly interface with at least oneof the WTRU 102 c, to facilitate access to one or more communicationnetworks, such as the core network 106/107/109, the Internet 110, and/orthe other networks 112. TRPs 119 a, 119 b may be any type of deviceconfigured to wirelessly interface with at least one of the WTRU 102 d,to facilitate access to one or more communication networks, such as thecore network 106/107/109, the Internet 110, and/or the other networks112. By way of example, the base stations 114 a, 114 b may be a basetransceiver station (BTS), a Node-B, an eNode B, a Home Node B, a HomeeNode B, a site controller, an access point (AP), a wireless router, andthe like. While the base stations 114 a, 114 b are each depicted as asingle element, it will be appreciated that the base stations 114 a, 114b may include any number of interconnected base stations and/or networkelements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 b may be part of the RAN103 b/104 b/105 b, which may also include other base stations and/ornetwork elements (not shown), such as a base station controller (BSC), aradio network controller (RNC), relay nodes, etc. The base station 114 amay be configured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The base station 114 b may be configured to transmit and/orreceive wired and/or wireless signals within a particular geographicregion, which may be referred to as a cell (not shown). The cell mayfurther be divided into cell sectors. For example, the cell associatedwith the base station 114 a may be divided into three sectors. Thus, inan embodiment, the base station 114 a may include three transceivers,e.g., one for each sector of the cell. In an embodiment, the basestation 114 a may employ multiple-input multiple output (MIMO)technology and, therefore, may utilize multiple transceivers for eachsector of the cell.

The base stations 114 a may communicate with one or more of the WTRUs102 a, 102 b, 102 c over an air interface 115/116/117, which may be anysuitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, cmWave,mmWave, etc.). The air interface 115/116/117 may be established usingany suitable radio access technology (RAT).

The base stations 114 b may communicate with one or more of the RRHs 118a, 118 b and/or TRPs 119 a, 119 b over a wired or air interface 115b/116 b/117 b, which may be any suitable wired (e.g., cable, opticalfiber, etc.) or wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, cmWave,mmWave, etc.). The air interface 115 b/116 b/117 b may be establishedusing any suitable radio access technology (RAT).

The RRHs 118 a, 118 b and/or TRPs 119 a, 119 b may communicate with oneor more of the WTRUs 102 c, 102 d over an air interface 115 c/116 c/117c, which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, cmWave, mmWave, etc.). The air interface 115 c/116 c/117 c may beestablished using any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b in the RAN103 b/104 b/105 b and the WTRUs 102 c, 102 d, may implement a radiotechnology such as Universal Mobile Telecommunications System (UMTS)Terrestrial Radio Access (UTRA), which may establish the air interface115/116/117 or 115 c/116 c/117 c respectively using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b in the RAN 103 b/104 b/105b and the WTRUs 102 c, 102 d, may implement a radio technology such asEvolved UMTS Terrestrial Radio Access (E-UTRA), which may establish theair interface 115/116/117 or 115 c/116 c/117 c respectively using LongTerm Evolution (LTE) and/or LTE-Advanced (LTE-A). In the future, the airinterface 115/116/117 may implement 3GPP NR technology.

In an embodiment, the base station 114 a in the RAN 103/104/105 and theWTRUs 102 a, 102 b, 102 c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b inthe RAN 103 b/104 b/105 b and the WTRUs 102 c, 102 d, may implementradio technologies such as IEEE 802.16 (e.g., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 c in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In anembodiment, the base station 114 c and the WTRUs 102 e, may implement aradio technology such as IEEE 802.11 to establish a wireless local areanetwork (WLAN). In an embodiment, the base station 114 c and the WTRUs102 d, may implement a radio technology such as IEEE 802.15 to establisha wireless personal area network (WPAN). In yet another embodiment, thebase station 114 c and the WTRUs 102 e, may utilize a cellular-based RAT(e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocellor femtocell. As shown in FIG. 1A, the base station 114 b may have adirect connection to the Internet 110. Thus, the base station 114 c maynot be required to access the Internet 110 via the core network106/107/109.

The RAN 103/104/105 and/or RAN 103 b/104 b/105 b may be in communicationwith the core network 106/107/109, which may be any type of networkconfigured to provide voice, data, applications, and/or voice overinternet protocol (VoIP) services to one or more of the WTRUs 102 a, 102b, 102 c, 102 d. For example, the core network 106/107/109 may providecall control, billing services, mobile location-based services, pre-paidcalling, Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication.

Although not shown in FIG. 1A, it will be appreciated that the RAN103/104/105 and/or RAN 103 b/104 b/105 b and/or the core network106/107/109 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 103/104/105 and/or RAN 103 b/104b/105 b or a different RAT. For example, in addition to being connectedto the RAN 103/104/105 and/or RAN 103 b/104 b/105 b, which may beutilizing an E-UTRA radio technology, the core network 106/107/109 mayalso be in communication with another RAN (not shown) employing a GSMradio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d, 102 e to access the PSTN 108, the Internet110, and/or other networks 112. The PSTN 108 may includecircuit-switched telephone networks that provide plain old telephoneservice (POTS). The Internet 110 may include a global system ofinterconnected computer networks and devices that use commoncommunication protocols, such as the transmission control protocol(TCP), user datagram protocol (UDP) and the internet protocol (IP) inthe TCP/IP internet protocol suite. The networks 112 may include wiredor wireless communications networks owned and/or operated by otherservice providers. For example, the networks 112 may include anothercore network connected to one or more RANs, which may employ the sameRAT as the RAN 103/104/105 and/or RAN 103 b/104 b/105 b or a differentRAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, 102 d, and 102 e may include multipletransceivers for communicating with different wireless networks overdifferent wireless links. For example, the WTRU 102 e shown in FIG. 1Amay be configured to communicate with the base station 114 a, which mayemploy a cellular-based radio technology, and with the base station 114c, which may employ an IEEE 802 radio technology.

FIG. 1B is a block diagram of an example apparatus or device configuredfor wireless communications in accordance with the embodimentsillustrated herein, such as for example, a WTRU 102. As shown in FIG.1B, the example WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad/indicators 128, non-removable memory 130, removablememory 132, a power source 134, a global positioning system (GPS)chipset 136, and other peripherals 138. It will be appreciated that theWTRU 102 may include any sub-combination of the foregoing elements whileremaining consistent with an embodiment. Also, embodiments contemplatethat the base stations 114 a and 114 b, and/or the nodes that basestations 114 a and 114 b may represent, such as but not limited to,transceiver station (BTS), a Node-B, a site controller, an access point(AP), a home node-B, an evolved home node-B (eNodeB), a home evolvednode-B (HeNB), a home evolved node-B gateway, and proxy nodes, amongothers, may include some or all of the elements depicted in FIG. 1B anddescribed herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in an embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. Although not shown in FIG. 1A, itwill be appreciated that the RAN 103/104/105 and/or the core network106/107/109 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 103/104/105 or a different RAT. Forexample, in addition to being connected to the RAN 103/104/105, whichmay be utilizing an E-UTRA radio technology, the core network106/107/109 may also be in communication with another RAN (not shown)employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, and 102 d may include multiple transceiversfor communicating with different wireless networks over differentwireless links. For example, the WTRU 102 c shown in FIG. 1A may beconfigured to communicate with the base station 114 a, which may employa cellular-based radio technology, and with the base station 114 b,which may employ an IEEE 802 radio technology.

FIG. 1B is a block diagram of an example apparatus or device configuredfor wireless communications in accordance with the embodimentsillustrated herein, such as for example, a WTRU 102. As shown in FIG.1B, the example WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad/indicators 128, non-removable memory 130, removablememory 132, a power source 134, a global positioning system (GPS)chipset 136, and other peripherals 138. It will be appreciated that theWTRU 102 may include any sub-combination of the foregoing elements whileremaining consistent with an embodiment. Also, embodiments contemplatethat the base stations 114 a and 114 b, and/or the nodes that basestations 114 a and 114 b may represent, such as but not limited totransceiver station (BTS), a Node-B, a site controller, an access point(AP), a home node-B, an evolved home node-B (eNodeB), a home evolvednode-B (HeNB), a home evolved node-B gateway, and proxy nodes, amongothers, may include some or all of the elements depicted in FIG. 1B anddescribed herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in an embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In an embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet an embodiment, the transmit/receive element 122 may be configuredto transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in an embodiment, the WTRU 102 may includetwo or more transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad/indicators 128 (e.g., a liquid crystal display(LCD) display unit or organic light-emitting diode (OLED) display unit).The processor 118 may also output user data to the speaker/microphone124, the keypad 126, and/or the display/touchpad/indicators 128. Inaddition, the processor 118 may access information from, and store datain, any type of suitable memory, such as the non-removable memory 130and/or the removable memory 132. The non-removable memory 130 mayinclude random-access memory (RAM), read-only memory (ROM), a hard disk,or any other type of memory storage device. The removable memory 132 mayinclude a subscriber identity module (SIM) card, a memory stick, asecure digital (SD) memory card, and the like. In an embodiment, theprocessor 118 may access information from, and store data in, memorythat is not physically located on the WTRU 102, such as on a server or ahome computer (not shown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries, solar cells, fuel cells, and thelike.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include varioussensors such as an accelerometer, biometrics (e.g., finger print)sensors, an e-compass, a satellite transceiver, a digital camera (forphotographs or video), a universal serial bus (USB) port or otherinterconnect interfaces, a vibration device, a television transceiver, ahands free headset, a Bluetooth® module, a frequency modulated (FM)radio unit, a digital music player, a media player, a video game playermodule, an Internet browser, and the like.

The WTRU 102 may be embodied in other apparatuses or devices, such as asensor, consumer electronics, a wearable device such as a smart watch orsmart clothing, a medical or eHealth device, a robot, industrialequipment, a drone, a vehicle such as a car, truck, train, or airplane.The WTRU 102 may connect to other components, modules, or systems ofsuch apparatuses or devices via one or more interconnect interfaces,such as an interconnect interface that may comprise one of theperipherals 138.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, and102 c over the air interface 115. The RAN 103 may also be incommunication with the core network 106. As shown in FIG. 1C, the RAN103 may include Node-Bs 140 a, 140 b, 140 c, which may each include oneor more transceivers for communicating with the WTRUs 102 a, 102 b, 102c over the air interface 115. The Node-Bs 140 a, 140 b, 140 c may eachbe associated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macro-diversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, and102 c over the air interface 116. The RAN 104 may also be incommunication with the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In an embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, and 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, and160 c in the RAN 104 via an S1 interface and may serve as a controlnode. For example, the MME 162 may be responsible for authenticatingusers of the WTRUs 102 a, 102 b, 102 c, bearer activation/deactivation,selecting a particular serving gateway during an initial attach of theWTRUs 102 a, 102 b, 102 c, and the like. The MME 162 may also provide acontrol plane function for switching between the RAN 104 and other RANs(not shown) that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, and 160 c in the RAN 104 via the S1 interface. The servinggateway 164 may generally route and forward user data packets to/fromthe WTRUs 102 a, 102 b, 102 c. The serving gateway 164 may also performother functions, such as anchoring user planes during inter-eNode Bhandovers, triggering paging when downlink data is available for theWTRUs 102 a, 102 b, 102 c, managing and storing contexts of the WTRUs102 a, 102 b, 102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, and 102 c over the air interface 117. As will befurther discussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell in the RAN 105 andmay include one or more transceivers for communicating with the WTRUs102 a, 102 b, 102 c over the air interface 117. In an embodiment, thebase stations 180 a, 180 b, 180 c may implement MIMO technology. Thus,the base station 180 a, for example, may use multiple antennas totransmit wireless signals to, and receive wireless signals from, theWTRU 102 a. The base stations 180 a, 180 b, 180 c may also providemobility management functions, such as handoff triggering, tunnelestablishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, and102 c may establish a logical interface (not shown) with the corenetwork 109. The logical interface between the WTRUs 102 a, 102 b, 102 cand the core network 109 may be defined as an R2 reference point, whichmay be used for authentication, authorization, IP host configurationmanagement, and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,and 180 c may be defined as an R8 reference point that includesprotocols for facilitating WTRU handovers and the transfer of databetween base stations. The communication link between the base stations180 a, 180 b, 180 c and the ASN gateway 182 may be defined as an R6reference point. The R6 reference point may include protocols forfacilitating mobility management based on mobility events associatedwith each of the WTRUs 102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, and 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

The core network entities described herein and illustrated in FIGS. 1A,1C, 1D, and 1E are identified by the names given to those entities incertain existing 3GPP specifications, but it is understood that in thefuture those entities and functionalities may be identified by othernames and certain entities or functions may be combined in futurespecifications published by 3GPP, including future 3GPP NRspecifications. Thus, the particular network entities andfunctionalities described and illustrated in FIGS. 1A, 1B, 1C, 1D, and1E are provided by way of example only, and it is understood that thesubject matter disclosed and claimed herein may be embodied orimplemented in any similar communication system, whether presentlydefined or defined in the future.

FIG. 1F is a block diagram of an exemplary computing system 90 in whichone or more apparatuses of the communications networks illustrated inFIGS. 1A, 1C, 1D and 1E may be embodied, such as certain nodes orfunctional entities in the RAN 103/104/105, Core Network 106/107/109,PSTN 108, Internet 110, or Other Networks 112. Computing system 90 maycomprise a computer or server and may be controlled primarily bycomputer readable instructions, which may be in the form of software,wherever, or by whatever means such software is stored or accessed. Suchcomputer readable instructions may be executed within a processor 91, tocause computing system 90 to do work. The processor 91 may be a generalpurpose processor, a special purpose processor, a conventionalprocessor, a digital signal processor (DSP), a plurality ofmicroprocessors, one or more microprocessors in association with a DSPcore, a controller, a microcontroller, Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, anyother type of integrated circuit (IC), a state machine, and the like.The processor 91 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the computing system 90 to operate in a communications network.Coprocessor 81 is an optional processor, distinct from main processor91, that may perform additional functions or assist processor 91.Processor 91 and/or coprocessor 81 may receive, generate, and processdata related to the methods and apparatuses disclosed herein.

In operation, processor 91 fetches, decodes, and executes instructions,and transfers information to and from other resources via the computingsystem's main data-transfer path, system bus 80. Such a system busconnects the components in computing system 90 and defines the mediumfor data exchange. System bus 80 typically includes data lines forsending data, address lines for sending addresses, and control lines forsending interrupts and for operating the system bus. An example of sucha system bus 80 is the PCI (Peripheral Component Interconnect) bus.

Memories coupled to system bus 80 include random access memory (RAM) 82and read only memory (ROM) 93. Such memories include circuitry thatallows information to be stored and retrieved. ROMs 93 generally containstored data that cannot easily be modified. Data stored in RAM 82 can beread or changed by processor 91 or other hardware devices. Access to RAM82 and/or ROM 93 may be controlled by memory controller 92. Memorycontroller 92 may provide an address translation function thattranslates virtual addresses into physical addresses as instructions areexecuted. Memory controller 92 may also provide a memory protectionfunction that isolates processes within the system and isolates systemprocesses from user processes. Thus, a program running in a first modecan access only memory mapped by its own process virtual address space;it cannot access memory within another process's virtual address spaceunless memory sharing between the processes has been set up.

In addition, computing system 90 may contain peripherals controller 83responsible for communicating instructions from processor 91 toperipherals, such as printer 94, keyboard 84, mouse 95, and disk drive85.

Display 86, which is controlled by display controller 96, is used todisplay visual output generated by computing system 90. Such visualoutput may include text, graphics, animated graphics, and video. Thevisual output may be provided in the form of a graphical user interface(GUI). Display 86 may be implemented with a CRT-based video display, anLCD-based flat-panel display, gas plasma-based flat-panel display, or atouch-panel. Display controller 96 includes electronic componentsrequired to generate a video signal that is sent to display 86.

Further, computing system 90 may contain communication circuitry, suchas for example a network adapter 97, that may be used to connectcomputing system 90 to an external communications network, such as theRAN 103/104/105, Core Network 106/107/109, PSTN 108, Internet 110, orOther Networks 112 of FIGS. 1A, 1B, 1C, 1D, and 1E, to enable thecomputing system 90 to communicate with other nodes or functionalentities of those networks. The communication circuitry, alone or incombination with the processor 91, may be used to perform thetransmitting and receiving steps of certain apparatuses, nodes, orfunctional entities described herein.

It is understood that any or all of the apparatuses, systems, methodsand processes described herein may be embodied in the form of computerexecutable instructions (e.g., program code) stored on acomputer-readable storage medium which instructions, when executed by aprocessor, such as processors 118 or 91, cause the processor to performand/or implement the systems, methods and processes described herein.Specifically, any of the steps, operations or functions described hereinmay be implemented in the form of such computer executable instructions,executing on the processor of an apparatus or computing systemconfigured for wireless and/or wired network communications. Computerreadable storage media include volatile and nonvolatile, removable andnon-removable media implemented in any non-transitory (e.g., tangible orphysical) method or technology for storage of information, but suchcomputer readable storage media do not includes signals. Computerreadable storage media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other tangible or physical medium which can be used to store thedesired information and which can be accessed by a computing system.

NextGen Network Requirements

3GPP TR 38.913 defines scenarios and requirements for next generationaccess technologies. The Key Performance Indicators (KPIs) for eMBB,URLLC and mMTC devices are summarized in Table 2.

TABLE 2 Device KPI Description Requirement eMBB Peak data Peak data rateis the highest theoretical data rate which 20 Gbps for rate is thereceived data bits assuming error-free conditions downlink andassignable to a single mobile station, when all 10 Gbps for assignableradio resources for the corresponding link uplink direction are utilized(i.e., excluding radio resources that are used for physical layersynchronization, reference signals or pilots, guard bands and guardtimes). Mobility Mobility interruption time means the shortest time 0 msfor intra- interruption duration supported by the system during which auser system time terminal cannot exchange user plane packets with anymobility base station during transitions. Data Plane For eMBB value, theevaluation needs to consider all 4 ms for UL, Latency typical delaysassociated with the transfer of the data and 4 ms for packets in anefficient way (e.g. applicable procedural DL delay when resources arenot pre-allocated, averaged HARQ retransmission delay, impacts ofnetwork architecture). URLLC Control Control plane latency refers to thetime to move from a 10 ms Plane battery efficient state (e.g., IDLE) tostart of Latency continuous data transfer (e.g., ACTIVE). Data Plane ForURLLC the target for user plane latency for UL 0.5 ms Latency and DL.Furthermore, if possible, the latency should also be low enough tosupport the use of the next generation access technologies as a wirelesstransport technology that can be used within the next generation accessarchitecture. Reliability Reliability can be evaluated by the successprobability 1-10⁻⁵ of transmitting X bytes within 1 ms, which is thetime within 1 ms it takes to deliver a small data packet from the radioprotocol layer 2/3 SDU ingress point to the radio protocol layer 2/3 SDUpoint of the radio interface, at a certain channel quality (e.g.,coverage-edge). mMTC Coverage MaxCL in uplink and downlink betweendevice and 164 dB Base Station site (antenna connector(s)) for a datarate of 160 bps, where the data rate is observed at the egress/ingresspoint of the radio protocol stack in uplink and downlink. UE Battery UEbattery life can be evaluated by the battery life of 15 years Life theUE without recharge. For mMTC, UE battery life in extreme coverage shallbe based on the activity of mobile originated data transfer consistingof 200 bytes UL per day followed by 20 bytes DL from MaxCL of 164 dB,assuming a stored energy capacity of 5 Wh. Connection Connection densityrefers to total number of devices 10⁶ devices/km² Density fulfillingspecific Quality of Service (QoS) per unit area (per km²). QoSdefinition should take into account the amount of data or access requestgenerated within a time t_gen that can be sent or received within agiven time, t_sendrx, with x% probability.LTE Random Access Procedure

In LTE, the random access procedure is performed for the followingevents: Initial access from RRC_IDLE; RRC Connection Re-establishmentprocedure; Handover; DL data arrival during RRC_CONNECTED requiringrandom access procedure (e.g., when UL synchronization status is“non-synchronized”); UL data arrival during RRC_CONNECTED requiringrandom access procedure (e.g., when UL synchronization status is“non-synchronized” or there are no PUCCH resources for SR available);and for positioning purpose during RRC_CONNECTED requiring random accessprocedure (e.g., when timing advance is needed for UE positioning).

The random access procedure takes two distinct forms: Contention based(applicable to first five events); and Non-contention based (applicableto only handover, DL data arrival, positioning and obtaining timingadvance alignment for a Secondary Timing Advance Group (sTAG)).

Contention based random access uses a 4-step procedure as shown FIG. 2.Each of the four steps is denoted by an Arabic numeral as follows:

1. Random Access Preamble on RACH in uplink. Transmission of RACHpreamble, allowing eNB to estimate the transmission timing of the UE.

2. Random Access Response generated by MAC on DL-SCH. Network transmitsa timing advance command to adjust the UE transmit timing. The networkalso assigns UL resources to the UE to be used in Step 3.

3. First scheduled UL transmission on UL-SCH. Transmission of themobile-terminal identity to the network using the UL-SCH.

4. Contention Resolution on DL. Transmission of a contention-resolutionmessage from the network to the UE on the DL-SCH.

Contention-free random access is only used for re-establishing uplinksynchronization upon downlink data arrival, handover and positioning.Only the first two steps of the procedure above are applicable, as thereis no need for contention resolution when performing the contention-freerandom access procedure.

A more detailed description of the random access procedure from the PHYand MAC layer perspectives is available in 3GPP TS 36.213 and 3GPP TS36.321 respectively.

The Physical Random Access Channel (PRACH) configuration in the systemand the generic random access parameters are specified in thePRACH-Config and RACH-ConfigCommon IEs of SIB2 shown below.

-- ASN1START RACH-ConfigCommon ::= SEQUENCE { preambleInfo SEQUENCE {numberOfRA-Preambles ENUMERATED { n4, n8, n12, n16 ,n20, n24, n28, n32,n36, n40, n44, n48, n52, n56, n60, n64}, preamblesGroupAConfig SEQUENCE{ sizeOfRA-PreamblesGroupA ENUMERATED { n4, n8, n12, n16 ,n20, n24, n28,n32, n36, n40, n44, n48, n52, n56, n60}, messageSizeGroupA ENUMERATED{b56, b144, b208, b256}, messagePowerOffsetGroupB ENUMERATED {minusinfinity, dB0, dB5, dB8, dB10, dB12, dB15, dB18}, ... } OPTIONAL --Need OP }, powerRampingParameters PowerRampingParameters,ra-SupervisionInfo SEQUENCE { preambleTransMax PreambleTransMax,ra-ResponseWindowSize ENUMERATED { sf2, sf3, sf4, sf5, sf6, sf7, sf8,sf10}, mac-ContentionResolutionTimer ENUMERATED { sf8, sf16, sf24, sf32,sf40, sf48, sf56, sf64} }, maxHARQ-Msg3Tx INTEGER (1..8), ... }RACH-ConfigCommon-v1250 ::= SEQUENCE { txFailParams-r12 SEQUENCE {connEstFailCount-r12 ENUMERATED {n1, n2, n3, n4},connEstFailOffsetValidity-r12 ENUMERATED {s30, s60, s120, s240, s300,s420, s600, s900}, connEstFailOffset-r12 INTEGER (0..15) OPTIONAL-- NeedOP } } RACH-ConfigCommonSCell-r11 ::= SEQUENCE {powerRampingParameters-r11 PowerRampingParameters,ra-SupervisionInfo-r11 SEQUENCE { preambleTransMax-r11 PreambleTransMax}, ... } PowerRampingParameters ::= SEQUENCE { powerRampingStepENUMERATED {dB0, dB2,dB4, dB6}, preambleInitialReceivedTargetPowerENUMERATED { dBm-120, dBm-118, dBm-116, dBm-114, dBm-112, dBm-110,dBm-108, dBm-106, dBm-104, dBm-102, dBm-100, dBm-98, dBm-96, dBm-94,dBm-92, dBm-90} } PreambleTransMax ::= ENUMERATED { n3, n4, n5, n6, n7,n8, n10, n20, n50, n100, n200} -- ASN1STOP -- ASN1START PRACH-ConfigSIB::= SEQUENCE { rootSequenceIndex INTEGER (0..837), prach-ConfigInfoPRACH-ConfigInfo } PRACH-Config ::= SEQUENCE { rootSequenceIndex INTEGER(0..837), prach-ConfigInfo PRACH-ConfigInfo OPTIONAL-- Need ON }PRACH-ConfigSCell-r10 ::= SEQUENCE { prach-ConfigIndex-r10 INTEGER(0..63) } PRACH-ConfigInfo ::= SEQUENCE { prach-ConfigIndex INTEGER(0..63), highSpeedFlag BOOLEAN, zeroCorrelationZoneConfig INTEGER(0..15), prach-FreqOffset INTEGER (0..94) } -- ASN1STOP

The IE RACH-ConfigDedicated is used to specify the dedicated randomaccess parameters as shown below.

-- ASN1START RACH-ConfigDedicated ::= SEQUENCE { ra-PreambleIndexINTEGER (0..63), ra-PRACH-MaskIndex INTEGER (0..15) } -- ASN1STOP

The PRACH mask index values are defined in Table 3 below.

TABLE 3 PRACH Mask Index Allowed PRACH (FDD) Allowed PRACH (TDD) 0 AllAll 1 PRACH Resource Index 0 PRACH Resource Index 0 2 PRACH ResourceIndex 1 PRACH Resource Index 1 3 PRACH Resource Index 2 PRACH ResourceIndex 2 4 PRACH Resource Index 3 PRACH Resource Index 3 5 PRACH ResourceIndex 4 PRACH Resource Index 4 6 PRACH Resource Index 5 PRACH ResourceIndex 5 7 PRACH Resource Index 6 Reserved 8 PRACH Resource Index 7Reserved 9 PRACH Resource Index 8 Reserved 10 PRACH Resource Index 9Reserved 11 Every, in the time domain, Every, in the time domain, evenPRACH opportunity even PRACH opportunity 1^(st) PRACH Resource 1^(st)PRACH Resource Index in subframe Index in subframe 12 Every, in the timedomain, Every, in the time domain, odd PRACH opportunity odd PRACHopportunity 1^(st) PRACH Resource 1^(st) PRACH Resource Index insubframe Index in subframe 13 Reserved 1^(st) PRACH Resource Index insubframe 14 Reserved 2^(nd) PRACH Resource Index in subframe 15 Reserved3^(rd) PRACH Resource Index in subframeNR Beamformed Access

Currently, 3GPP standardization's efforts are underway to design theframework for beamformed access. The characteristics of the wirelesschannel at higher frequencies are significantly different from the sub-6GHz channel that LTE is currently deployed on. The key challenge ofdesigning the new Radio Access Technology (RAT) for higher frequencieswill be in overcoming the larger path-loss at higher frequency bands. Inaddition to this larger path-loss, the higher frequencies are subject toan unfavorable scattering environment due to blockage caused by poordiffraction. Therefore, MIMO/beamforming is essential in guaranteeingsufficient signal level at the receiver end.

Relying solely on MIMO digital precoding used by digital BF tocompensate for the additional path-loss in higher frequencies seems notenough to provide similar coverage as below 6 GHz. Thus, the use ofanalog beamforming for achieving additional gain can be an alternativein conjunction with digital beamforming. A sufficiently narrow beamshould be formed with lots of antenna elements, which is likely to bequite different from the one assumed for the LTE evaluations. For largebeamforming gain, the beam-width correspondingly tends to be reduced,and hence the beam with the large directional antenna gain cannot coverthe whole horizontal sector area specifically in a 3-sectorconfiguration. The limiting factors of the number of concurrent highgain beams include the cost and complexity of the transceiverarchitecture.

From these observations above, multiple transmissions in time domainwith narrow coverage beams steered to cover different serving areas arenecessary. Inherently, the analog beam of a subarray can be steeredtoward a single direction at the time resolution of an OFDM symbol orany appropriate time interval unit defined for the purpose of beamsteering across different serving areas within the cell, and hence thenumber of subarrays determines the number of beam directions and thecorresponding coverage on each OFDM symbol or time interval unit definedfor the purpose of beams steering. In some literature, the provision ofmultiple narrow coverage beams for this purpose has been called “beamsweeping”. For analog and hybrid beamforming, the beam sweeping seems tobe essential to provide the basic coverage in NR. This concept isillustrated in FIG. 3 where the coverage of a sector level cell isachieved with sectors beams and multiple high gain narrow beams. Also,for analog and hybrid beamforming with massive MIMO, multipletransmissions in time domain with narrow coverage beams steered to coverdifferent serving areas is essential to cover the whole coverage areaswithin a serving cell in NR.

One concept closely related to beam sweeping is the concept of beampairing which is used to select the best beam pair between a UE and itsserving cell, which can be used for control signaling or datatransmission. In some embodiments, the best beam pair may include a beampair above a predetermined threshold. For the downlink transmission, abeam pair will consist of UE RX beam and NR-Node TX beam while foruplink transmission, a beam pair will consist of UE TX beam and NR-NodeRX beam.

Another related concept is the concept of beam training which is usedfor beam refinement. For example, as illustrated in FIG. 3, a coarsersector beamforming may be applied during the beam sweeping and sectorbeam pairing procedure. A beam training may then follow where forexample the antenna weights vector is refined, followed by the pairingof high gain narrow beams between the UE and NR-Node.

NR System Information

System Information (SI) is divided into Minimum SI and Other SI. MinimumSI is periodically broadcast and comprises basic information requiredfor initial access and information for acquiring any other SI broadcastperiodically or provisioned on-demand, i.e. scheduling information. TheOther SI encompasses everything not broadcast in the Minimum SI and mayeither be broadcast, or provisioned in a dedicated manner, eithertriggered by the network or upon request from the UE as illustrated inFIG. 4.

For UEs in RRC_CONNECTED, dedicated RRC signaling is used for therequest and delivery of the Other SI. For UEs in RRC_IDLE andRRC_INACTIVE, the request triggers a random access procedure and iscarried over MSG3 unless the requested SI is associated to a subset ofthe PRACH resources, in which case MSG1 can be used. When MSG1 is used,the minimum granularity of the request is one SI message (i.e., a set ofSIBs) and one RACH preamble can be used to request multiple SI messages.The gNB acknowledges the request in MSG2.

The Other SI may be broadcast at a configurable periodicity and for acertain duration. It is a network decision whether the other SI isbroadcast or delivered through dedicated and UE specific RRC signaling.Each cell on which the UE is allowed to camp broadcasts at least somecontents of the Minimum SI, while there may be cells in the system onwhich the UE cannot camp and do not broadcast the Minimum SI.

For a cell/frequency that is considered for camping by the UE, the UE isnot required to acquire the contents of the minimum SI of thatcell/frequency from another cell/frequency layer. This does not precludethe case that the UE applies stored SI from previously visited cell(s).If the UE cannot determine the full contents of the minimum SI of a cell(by receiving from that cell or from valid stored SI from previouscells), the UE shall consider that cell as barred.

When multiple numerologies are mixed on a single carrier, only thedefault one is used for system information broadcast and paging. FFS iswhether initial access from RRC_INACTIVE also relies on the defaultnumerology.

NR UE States and State Transitions

A UE is either in RRC_CONNECTED state or in RRC_INACTIVE state when anRRC connection has been established. If this is not the case, i.e. noRRC connection is established, the UE is in RRC_IDLE state. The RRCstates can further be characterized as follows:

1. During RRC_IDLE, the following may occur:

a UE specific DRX may be configured by upper layers;

UE controlled mobility based on network configuration;

The UE: Monitors a Paging channel; Performs neighboring cellmeasurements and cell (re-)selection; and Acquires system information.

2. During RRC_INACTIVE, the following may occur:

A UE specific DRX may be configured by upper layers or by RRC layer;

UE controlled mobility based on network configuration;

The UE stores the AS context;

The UE: Monitors a Paging channel; Performs neighboring cellmeasurements and cell (re-)selection; Performs RAN-based notificationarea updates when moving outside the RAN-based notification area (FFSWhether a RAN-based notification area is always configured or not; andFFS UE behavior if it is decided that a RAN-based notification area isnot always configured); and Acquires system information.

3. During RRC_CONNECTED, the following occur:

The UE stores the AS context;

Transfer of unicast data to/from UE;

At lower layers, the UE may be configured with a UE specific DRX;

For UEs supporting CA, use of one or more SCells, aggregated with thePCell, for increased bandwidth;

For UEs supporting DC, use of one SCG, aggregated with the MCG, forincreased bandwidth;

Network controlled mobility, i.e. handover within NR and to/fromE-UTRAN.

The UE: Monitors a Paging channel; Monitors control channels associatedwith the shared data channel to determine if data is scheduled for it;Provides channel quality and feedback information; Performs neighboringcell measurements and measurement reporting; Acquires systeminformation.

As shown in FIG. 5, an overview of UE RRC state machine and statetransitions in NR is provided. A UE has only one RRC state in NR at onetime.

FIG. 6 illustrates an overview of UE state machine and state transitionsin NR as well as the mobility procedures supported between NR/NGC andE-UTRAN/EPC. The UE state machine, state transition and mobilityprocedures between NR/NGC and E-UTRA/NGC are FFS.

NR Mobility in RRC_CONNECTED

Network controlled mobility applies to UEs in RRC_CONNECTED and iscategorized into two types of mobility: cell level mobility and beamlevel mobility. Cell level mobility requires explicit RRC signaling tobe triggered, i.e. handover. Beam level mobility does not requireexplicit RRC signaling to be triggered—it is dealt with at lowerlayers—and RRC is not required to know which beam is being used at agiven point in time.

FIG. 7 illustrates the C-plane handling of the basic handover scenariowhere neither the AMF nor the UPF changes. Each of the steps in FIG. 7is denoted by an Arabic numeral as follows:

0. The UE context within the source gNB contains information regardingroaming and access restrictions which were provided either at connectionestablishment or at the last TA update.

1. The source gNB configures the UE measurement procedures and the UEreports according to the measurement configuration.

2. The source gNB decides to handover the UE, based on MEASUREMENTREPORT and RRM information.

3. The source gNB issues a HANDOVER REQUEST message to the target gNBpassing necessary information to prepare the HO at the target side

4. Admission Control may be performed by the target gNB.

5. The target gNB prepares HO with L1/L2 and sends the HANDOVER REQUESTACKNOWLEDGE to the source gNB.

6. The target gNB generates the RRC message to perform the handover.

7. The source gNB sends the SN STATUS TRANSFER message to the targetgNB.

8. The UE synchronizes to the target cell and completes the RRC handoverprocedure.

9. The target gNB sends a PATH SWITCH REQUEST message to AMF to trigger5GC to switch the DL data path towards the target gNB and to establishan NG-C interface instance towards the target gNB.

10. 5GC switches the DL data path towards the target gNB

11. The AMF confirms the PATH SWITCH REQUEST message with the PATHSWITCH REQUEST ACKNOWLEDGE message.

12. By sending the UE CONTEXT RELEASE message, the target gNB informsthe source gNB about the success of HO and triggers the release ofresources by the source gNB. The target gNB sends this message after thePATH SWITCH REQUEST ACKNOWLEDGE message is received from the AMF. Uponreception of the UE CONTEXT RELEASE message, the source gNB can releaseradio and C-plane related resources associated to the UE context. Anyongoing data forwarding may continue.

According to another embodiment, beam management is defined as followsin NR:

Beam management: a set of L1/L2 procedures to acquire and maintain a setof TRP(s) and/or UE beams that can be used for DL and ULtransmission/reception, which include at least following aspects:

Beam determination: for TRP(s) or UE to select of its own Tx/Rx beam(s).

Beam measurement: for TRP(s) or UE to measure characteristics ofreceived beamformed signals.

Beam reporting: for UE to report information a property/quality ofbeamformed signal(s) based on beam measurement.

Beam sweeping: operation of covering a spatial area, with beamstransmitted and/or received during a time interval in a predeterminedway.

According to another embodiment, the following DL L1/L2 beam managementprocedures are supported within one or multiple TRPs:

P-1: is used to enable UE measurement on different TRP Tx beams tosupport selection of TRP Tx beams/UE Rx beam(s). For beamforming at TRP,it typically includes a intra/inter-TRP Tx beam sweep from a set ofdifferent beams. For beamforming at UE, it typically includes a UE Rxbeam sweep from a set of different beams.

P-2: is used to enable UE measurement on different TRP Tx beams topossibly change inter/intra-TRP Tx beam(s); From a possibly smaller setof beams for beam refinement than in P-1. Note that P-2 can be a specialcase of P-1.

P-3: is used to enable UE measurement on the same TRP Tx beam to changeUE Rx beam in the case UE uses beamforming.

RAN2 Agreements

In an embodiment, the following agreements related to measurementreporting in NR have been made. For Agreements from R2-97b:

1. In NR, as in LTE, it should be possible to include cell quality (e.g.RSRP and/or RSRQ) in the measurement report.

2. UE can indicate the SS block identifier (terminology to be confirmedby RAN1 LS) of x best beams where x is configurable in measurementreports triggered by the events on SS block. Specifically, (i) FFSwhether it is needed for all events; (ii) FFS how the UE can choose thebest beams; (iii) FFS whether quality of the beams are also reported;and (iv) FFS whether the same applies for CSI-RS.

For Agreements from R2-98:

1: SS block identifier is not included in measurement reportingtriggered by CSI-RS events.

2: SS block identifier can be included in measurement reportingtriggered by event A1-A6 for measurement reporting triggered by NR-SSevents. Specifically (i) FFS: How to select the x best beams to beincluded in the report; and (ii) FFS Whether x is the same value for thetriggered cell and the non-triggered cells.

Another agreement from R2-89 includes:

1: For SS based events, the UE report the beams in the order of quality.

2: CSI-RS identifier can be included in measurement reporting triggeredby event A1-A6 for measurement reporting triggered by CSI-RS events

3: for CSI-RS based events, the UE report the beams in the order ofquality.

FFS: For A1-A6 events triggered by CSI-RS, the cell quality derived fromNR-SS from the same cell can be included in the measurement report ifavailable based on other measurements that have been configured.

Agreements from R2-NR-AH #2 include:

1: Measurement report includes the measurement identity of theassociated measurement configuration that triggered the reporting

2: Cell measurement quantities can be included in the measurementreport. RAN1 to confirm the cell measurement quantities to be supported.

3: The cell measurement quantities to be included in the measurementreport are configurable by the network.

4: maxReportCells is supported to indicate the maximum number ofnon-serving cells to be reported by the UE (as in LTE).

5: For event triggered reporting: (i) PCell and SCells cell quality arealways included in the measurement report; and (ii) Include cells in thecellsTriggeredList in the measurement report (same as LTE). FFS cells tobe included according to cellsTriggeredList to be clarified

6 Blacklisted cells, if provided, are not used in event evaluation andreporting (as in LTE).

7 If whitelisted cells are provided, only whitelisted cells are used inevent evaluation and reporting (as in LTE).

8 Beam measurements (based on NR-SS and CSI-RS) can be included in themeasurement report and can be configured by the network (i.e. networkconfigures the UE to report beam identifier only, beam measurementresult and identifier, or no beam reporting)

9: Measurement quantities can be configured by the network for beammeasurement reporting. RAN1 to confirm the measurement quantities to besupported. FFS Whether the cell and beam measurement quantities to bereported need to be consistent.

10: For selection of x SS blocks to be included in the measurementreport for each cell: (i) x can be configured separately from N (N usedin cell quality derivation). FFS how to select the up to x SS blocks tobe included.

11: For cell events (A1 to A6 events), selection of y CSI-RS resource isincluded in the measurement report for each cell: (i) y can beconfigured separately from N (N used in cell quality derivation). FFShow to select the up to y CSI-RS resource to be included. FFSmeasurement report content for Cx events. FFS whether to include thecell quality derived from NR-SS for the same cell to be included in ameasurement report triggered based on CSI-RS, if the NR-SS measurementis available.

The following agreements related to connected mode mobility in NR havebeen made. In Agreements from R2-96:

1: NR shall support HO as part of the NR mobility procedures.

2: Network based mobility shall reuse the same principles as LTE(Rel-13) and for inter gNB HO consisting of at least: (i) Source gNBinitiates the HO over the Xn interface via a HO request; (ii) Target gNBperforms admission control and provides the RRC configuration as part ofthe HO acknowledgement; (iii) Source gNB provides the configuration tothe UE including the HO command via RRC; and (iv) The UE moves theconnection to the target gNB via RRC

According to another Agreement from R2-96:

1 At least cell id and all information required to access the targetcell will be included in the HO command.

2 For at least some cases information required for contention based andcontention free access can be included in the HO command

3 To be studied what beam related information of the target cell may berequired.

4 Study the possibility of handover where a condition configured by thegNB is used by the UE to determine when it executes the handover.

Yet another embodiment is directed to Agreements from R2-97. In oneagreement Access information (e.g. RACH configuration) for the targetcell is provided in the HO command to enable the UE to access the cellwithout reading system information. Access information may include beamspecific information (if any).

Yet another embodiment is directed to Agreements from R2-97b:

1. Handover command can contain at least cell identity of the targetcell and RACH configuration(s) associated to the beams of the targetcell. RACH configuration(s) can include configuration forcontention-free random access.

1b. UE selects a suitable beam from all beams of the target cell.

1c. UE performs CBRA on the UE's selected beam if CFRA resources are notprovided for the UE's selected beam.

Yet another agreement is directed from R2-NR-AH #2. Here, the Agreementincludes:

1 Measurement information (including beam information if there are beamsin the network) reported by the UE can be included the HANDOVER REQUESTmessage sent to the target.

2 The handover command includes all necessary parameters (at least newC-RNTI, target gNB security algorithm identifiers, and optionally a setof dedicated RACH resources (RAN2 understand this could betime/frequency/sequence but decision is up to RAN1), etc.). FFS How theUE uses the set of dedicated RACH resources and common RACH resources.In addition, FFS How the UE knows the common RACH resources.

3 Handover command can include association between RACH resources and SSblocks.

4 Handover command can include association between RACH resources andCSI-RS configuration(s), if RAN1 conclude that such association ispossible. FFS How the UE selects the beam and RACH resources to be usedto access from the information included in the handover command. Thiscould be specified behavior, or specified behavior with someparameter(s) than can be controlled by the network, and can be discussedis some aspects might be left to UE implementation.

5 Timer based handover failure procedure like LTE (T304) is supported inNR.

6 RRC connection re-establishment procedure should be used forrecovering handover failure.

Yet another agreement is directed to R2-99. In this agreement, theinformation is carried between the source and target node.

1. NR RRC specifications define a transparent RRC container (like theHandoverPreparationInformation message in LTE) to be transmitted fromthe source gNB to the target gNB as part of the Xn Handover Requestmessage.

2.1 As in LTE, the HandoverPreparationInformation to be transmitted fromthe source gNB to the target gNB includes the UE capabilities fordifferent RATs

2.2 As in LTE, the HandoverPreparationInformation to be transmitted fromthe source gNB to the target gNB can include the AS configuration, theRRM configuration and the AS context (including information necessary tohandle handover failures). The details of the content of each IE areFFS.

3.1: The AS configuration includes the measurement configuration andradio resource configurations, UE identifier in the source, at leastAntenna Info and DL Carrier Frequency. The FFS is whether the ASconfiguration includes the QoS flow to DRB mapping that was notconfigured to the UE via RRC signalling. The FFS may need to provide thesystem information from source equivalent to LTE's MIB, SIB-1 and SIB-2(some checking of use of this in LTE to be done).

4.1: The RRM configuration can include at least the inactive time.

4.2: As in LTE, to support CA case, the RRM configuration can includethe list of best cells on each frequency for which measurementinformation is available.

5 Available beam measurement information can be part of the RRMconfiguration of the HandoverPreparationInformation message if beammeasurement information (i.e. beam indexes and optionally measurementresults) have been configured by the source gNodeB to be reported by aUE. That information is not a mandatory part of theHandoverPreparationInformation message. For the FFS, for which cell(s)beam measurement information can be included e.g. only candidate targetcell.

6 The RRM configuration can include both beam measurement information(for layer 3 mobility) associated to SS Block(s) and CSI-RS(s) for thereported cell (or cells depending on outcome of FFS above) if both typesof measurements are available.

Agreements can also relate to content of handover command in RRCincluding the following:

1. The NR RRC specifications define a transparent RRC container (likethe Handover Command message in LTE) to be transmitted from the targetgNB to the source gNB as part of the Xn Handover Request Acknowledgementmessage.

2. As in LTE, the handover command should be entirely generated by thetarget gNB. In FFS, there could be exceptions for this (e.g., for MBBenhancement similar to that in LTE, if supported).

3 The mobilityControlInfo can contain at least the target physical cellidentifier (or equivalent defined by RAN1), the carrier frequency, theT304 like timer and the new UE identifier (C-RNTI type of identifier).

4 RAN2 understanding is that the common RACH configuration for beams inthe target cell can only be associated to the SS Block(s).

5 RAN2 understanding is that the network can have dedicated RACHconfigurations associated to the SS Block(s) and/or have dedicated RACHconfigurations associated to CSI-RS(s) within a cell. In FFS, the targetgNB can optionally include the common RACH configuration in themobilityControlInfo. If not included the UE continues to use the commonRACH configuration of the source cell.

6 The target gNB is able to include one of the following RACHconfigurations in the mobilityControlInfo to enable the UE to access thetarget cell: i/ Common RACH configuration, ii/ Common RACHconfiguration+Dedicated RACH configuration associated with SS-Block oriii/ Common RACH configuration+Dedicated RACH configuration associatedwith CSI-RS. (List of options to be revised if common RACH is concludedto be optional based on above FFS.) (Simultaneously including in themobilityControlInfo a dedicated RACH configuration associated withSS-Block and a dedicated RACH configuration associated with CSI-RS isnot supported). FFS whether there will be a fallback procedure usingcommon RACH when dedicated RACH fails.

Agreements can also relate to R2-99b as follows:

1. Dedicated RACH Resources (if provided) where the beam qualitymeasured on the associated NR-SS or CSI-RS is above a threshold areprioritized. Common NR-SS threshold and a dedicated NR-SS/CSI-RSthreshold, if required, is configured in handover command.

The order to access the dedicated RACH resources is up to UEimplementations.

Agreements for handover and PSCell change involving RACH include:

The UE shall not switch to contention-based RACH resources if there arededicated RACH resources fulfilling the quality threshold specifiedabove.

The same behavior as for LTE in T304 and T307 is provided here.

Measurement Reporting

In one embodiment, selection of ‘x’ SS-based best beams to report isdescribed. In case 1, SS based events, for e.g. event A1 to A6 triggeredby measurements of SS signals, is described. For SS based beams, the UEselects the x best beams to be included in the measurement report as thebest beam and the up to x-1 best beams above absolute configuredthreshold. The absolute threshold may be based on one or two measurementquantities: an RSRP threshold and an RSRQ threshold. The x best beamsmay be a subset of the beams used in the cell quality derivation.Further details are captured below.

1. If the configured threshold is RSRP only, then the UE selects thebest beam and the up to x-1 beams with the next x-1 largest RSRP valuesabove absolute configured threshold. In this case the best beam is thebeam with the highest measured RSRP value. Ties are resolved as follow:in one embodiment, the UE performs a random ranking between beams bi andbj. Alternatively, between two tied beams, the UE selects as betterbeam, the beam with the largest number of CSR-RS based beams withquality above absolute configured threshold is considered to be higherranked i.e. better beam. The quantity for the CSI-RS based qualityevaluation may be RSRP, RSRQ or both.

2. If the configured threshold is RSRQ only, then the UE selects thebest beam and the up to x-1 beams with the next x-1 largest RSRQ values.In this case the best beam is the beam with the highest measured RSRQvalue. Ties are resolved as follow: in one embodiment, the UE performs arandom ranking between beams bi and bj. Alternatively, between two tiesbeams, the UE selects as better beam, the beam with the largest numberof CSR-RS based beams with quality above absolute configured thresholdis considered to be higher ranked i.e. better beam. The quantity for theCSI-RS based quality evaluation may be RSRP, RSRQ or both.

3. If the configured threshold has both RSRP threshold value and RSRQthreshold value, the UE may apply the following criteria for theselection of the x best beams to report:

a. The UE ranks the N beams used in the evaluation of the cell qualityas follows: beam bi is better than beam bj if RSRP(bi)≥RSRP(bj) andRSRQ(bi)≥RSRQ(bj). The best beam is the beam with the highest rank. TheUE then selects the remaining up to x-1 best beams as the next x-1highest ranked beams with quality above a configured threshold in termsof both RSRP quantity and RSRQ quantity. In order to address scenarioswhere there are ties for ranking between beam bi and beam bj, we definetie as follow:

b. Beams bi and bj are tie for ranking as defined above, as per one ofthe following situations: RSRP(bi)=RSRP(bj) and RSRQ(bi)=RSRQ(bj) orRSRP(bi)>RSRP(bj) and RSRQ(bi)<RSRQ(bj) or RSRP(bi)<RSRP(bj) andRSRQ(bi)>RSRQ(bj).

c. The UE may resolve the tie using one of more of the followingapproaches:

(i) In one embodiment, the UE may be configured with a secondary rankingcriteria as follow: beam bi is ranked higher than beam bj i.e. beam biis better beam than bj if RSRP(bi)>RSRP(bj). Alternative criteria may bebeam bi is ranked higher than beam bj if RSRQ(bi)>than RSRQ(bj).

(ii) In another embodiment, the UE performs a random ordering between biand bj or alternatively, between two beams, the UE selects as betterbeam, the beam with the largest number of CSR-RS based beams withquality above absolute configured threshold is considered to be higherranked i.e. better beam. The quantity for the CSI-RS based qualityevaluation may be RSRP, RSRQ or both.

In case 2, CSI-RS based events, e.g., events A1 to A6 triggered bymeasurements of CSI-RS, are described. In one embodiment, the UEselected the x SS based best beams to include in the measurement reportas follow:

1. First the UE selects the y CSI-RS based best beams as per theprocedure described above for Case 1. The parameter y may be theconfigured number of CSI-RS based best beam to be included in themeasurement reports.

2. The UE selects as the up to x best SS based beams to report, the SSbased beams that correspond to the up to ‘y’ best CSI-RS based bestsbeam i.e. the up to ‘x’ SS based beams which contains the up to ‘y’ bestCSI-RS based beams selected above as their narrower beams.

In yet another embodiment, the UE may select up to ‘x’ SS-based bestbeams to include in the measurement report, using the proceduredescribed in case 1.

If configured by the network i.e. as per network configuration, the UEincludes in the measurement report, the x SS blocks corresponding to theselected x SS based best beams for measurement reporting purpose.

In yet another embodiment, selection of the ‘y’ best beams associatedwith CSI-RS is described. In case 1, CSI-RS based events, e.g., eventsA1 to A6 triggered by measurements of CSI-RS, are described. For CSI-RSbased beams, the UE selects they best beams to be included in themeasurement report as the best beam and the up to y-1 best beams aboveabsolute configured threshold. The absolute threshold may be based onone or two measurement quantities: an RSRP threshold and an RSRQthreshold. The y best beams may be a subset of the beams used in thecell quality derivation. Further details are captured below.

1. If the configured threshold is RSRP only, then the UE reports thebest beam and the up to y-1 beams with the next y-1 largest RSRP valuesabove absolute configured threshold. In this case the best beam is thebeam with the highest measured RSRP value. The UE resolves ties byperforming a random ranking between beams bi and bj.

2. If the configured threshold is RSRQ only, then the UE reports thebest beam and the up to y-1 beams with the next y-1 largest RSRQ values.In this case the best beam is the beam with the highest measured RSRQvalue. The UE resolves ties by performing a random ranking between beamsbi and bj.

3. If the configured threshold has both RSRP threshold value and RSRQthreshold value, the UE may apply the following criteria for theselection of the y best beams to report:

a. The UE ranks the N beams used in the evaluation of the cell qualityas follows: beam bi is better than beam bj if RSRP(bi)>RSRP(bj) andRSRQ(bi)>RSRQ(bj). The best beam is the beam with the highest rank. TheUE then selects the remaining up to y-1 best beams as the next y-1highest ranked beams with quality above a configured threshold in termsof both RSRP quantity and RSRQ quantity. In order to address scenarioswhere there ties for ranking between beam bi and beam bj, we define tieas follow:

b. Beams bi and bj are tie for ranking as defined above, as per one ofthe following situations: RSRP(bi)=RSRP(bj) and RSRQ(bi)=RSRQ(bj) orRSRP(bi)>RSRP(bj) and RSRQ(bi)<RSRQ(bj) or RSRP(bi)<RSRP(bj) andRSRQ(bi)>RSRQ(bj).

c. The UE may resolve the tie using one of more of the followingapproaches:

(i) In one embodiment, the UE may be configured with a secondary rankingcriteria as follow: beam bi is ranked higher than beam bj i.e. beam biis better beam than bj if RSRP(bi)>RSRP(bj). Alternative criteria may bebeam bi is ranked higher than beam bj if RSRQ(bi)>than RSRQ(bj).

(ii) In another embodiment, The UE resolves ties by performing a randomranking between beams bi and bj.

According to Case 2, SS based events, e.g., event A1 to A6 triggered bymeasurements of SS signals, are described. In one embodiment, the UEselected the y CSI-RS based best beams to include in the measurementreport as follows:

1. First the UE selects the x SS based best beams as per the proceduredescribed above. The parameter x may be the configured number of SSbased best beams to be included in the measurement reports.

2. The UE then selects as the up to ‘y’ best CSI-RS based beams toreport, the CSI-RS based beams that correspond to the up to x best SSbased best beams i.e. the up to y CSI-RS based beams, which are narrowbeams of the selected best SS based beams.

In another embodiment, the UE may select the up to y CSI-RS based bestbeams to include in the measurement report, using the proceduredescribed in case 1 of this section.

According to another embodiment, if configured by the network, i.e., asper network configuration, the UE includes in the measurement report,the y CSI-RS resources that correspond to the selected y CSI-RS basedbest beams for measurement reporting purpose.

PRACH Resource Selection

According to another aspect, solutions are proposed to optimally selectthe PRACH resource used for access to the target cell from the set ofdedicated and/or common PRACH resources configured by the network viadedicated signaling for e.g., the handover command or via broadcastsignal.

PRACH resource selection is performed prior to the first Msg1transmission and any subsequent Msg1 transmissions. Subsequent Msg1transmissions may occur if the UE receives a Random Access Response(RAR) that includes a Backoff Indicator (BI) subheader or if the RandomAccess procedure does not complete successfully. For instance, when aRandom Access Response (RAR) identified by the RA-RNTI associated withthe selected PRACH and containing a Random Access Preamble identifiercorresponding to the transmitted PREAMBLE_INDEX was not received duringthe RAR window.

For NR, the parameters for the dedicated RACH configuration may besignaled in the handover command using an NR-RACH-ConfigDedicated IEsuch as shown below. In addition to the Preamble Index and PRACH MaskIndex parameters, we propose to include parameters for the ID's of theDL beams associated with the dedicated PRACH resource(s). Either an SSBlock ID or a CSI-RS Configuration ID parameter is required to bepresent. It is also possible for both parameters to be present. If theCSI-RS Configuration ID parameter is present, a PRACH configurationassociated with the CSI-RS configuration may also be present.

-- ASN1START RACH-ConfigDedicated ::= SEQUENCE { ra-PreambleIndexINTEGER (0..63), ra-PRACH-MaskIndex INTEGER (0..15) OPTIONAL,ra-ssBlockId INTEGER (1..maxSSBlocks) OPTIONAL, -- cond ssBlockOrCsi-Rsra-csiRsCfgId INTEGER (1..maxCSI-RS-Cfg) OPTIONAL, -- condssBlockOrCsi-Rs prach-csiRsConfigInfo PRACH-ConfigInfo OPTIONAL -- condcsi-Rs } maxSSBlocks INTEGER ::= 64 -- Maximum number of SS blocks in anSS burst set maxCSI-RS-Cfg INTEGER ::= 32 -- Maximum number of CSI-RSconfigurations -- ASN1STOP

TABLE 4 NR-RACH-ConfigDedicated field descriptions ra-Preamble IndexExplicitly signalled Random Access Preamble for RA Resource selection.ra-PRACH-MaskIndex Explicitly signalled PRACH Mask Index for RA Resourceselection. ra-ssBlockId Explicitly signalled SS block Id for RA Resourceselection. ra-csi-RsCfgId Explicitly signalled CSI-RS configuration IDfor RA Resource selection. prach-csiRsConfigInfo Explicitly signalledPRACH configuration associated with CSI-RS configuration for RA Resourceselection.

TABLE 5 Conditional presence Explanation ssBlockOrCsi-Rs Either thera-ssBlockId or the ra-csiRsCfgId field mandatory. Both may also bepresent. csi-Rs This field is optionally present in the casera-csiRsCfgId is present.

An alternate NR-RACH-ConfigDedicated IE where different Preamble Indexand PRACH Mask Index parameters may be associated with each beam isshown below.

-- ASN1START RACH-ConfigDedicated ::= SEQUENCE {SIZE(1..maxDedicatedPRACHResources) ra-PreambleIndex INTEGER (0..63),ra-PRACH-MaskIndex INTEGER (0..15) OPTIONAL, ra-beamId CHOICE {ra-ssBlockId INTEGER (1..maxSSBlocks), ra-csiRsCfgId INTEGER(1..maxCSI-RS-Cfg) } prach-csiRsConfigInfo PRACH-ConfigInfo OPTIONAL --cond csi-Rs } maxSSBlocks INTEGER ::= 64 -- Maximum number of SS blocksin an SS burst set maxCSI-RS-Cfg INTEGER ::= 32 -- Maximum number ofCSI-RS configurations maxDedicatedPRACHResources INTEGER ::= 8 --Maximum number of dedicated PRACH resources -- ASN1STOP

An alternate NR-RACH-ConfigDedicated IE where the same Preamble Indexand PRACH Mask Index parameters associated with each beam are shownbelow.

-- ASN1START RACH-ConfigDedicated ::= SEQUENCE { ra-PreambleIndexINTEGER (0..63), ra-PRACH-MaskIndex INTEGER (0..15) OPTIONAL, ra-beamSEQUENCE { SIZE(1..maxDedicatedPRACHResources) ra-beamId CHOICE {ra-ssBlockId INTEGER (1..maxSSBlocks), ra-csiRsCfgId INTEGER(1..maxCSI-RS-Cfg) } prach-csiRsConfigInfo PRACH-ConfigInfo OPTIONAL --cond csi- Rs } } maxSSBlocks INTEGER ::= 64 -- Maximum number of SSblocks in an SS burst set maxCSI-RS-Cfg INTEGER ::= 32 -- Maximum numberof CSI-RS configurations maxDedicatedPRACHResources INTEGER ::= 8 --Maximum number of dedicated PRACH resources -- ASN1STOP

In an alternative embodiment, for the NR-RACH-ConfigDedicated IE, thededicated RACH configuration may be a Preamble Index. It mayalternatively include a list of SSBs where each SSB in the list isassociated with a Preamble Index and a list of PRACH resources. It mayalternatively include a list of CSI-RS configurations where each CSI-RSconfiguration in the list is associated with a Preamble Index and listof PRACH resources as shown below.

-- ASN1START RACH-ConfigDedicated ::= SEQUENCE { cfra-ResourcesCFRA-Resources } CFRA-Resources ::= CHOICE { cfra-ResourceCFRA-Resource, cfra-ssb-ResourceList CFRA-SSB-ResourceList,cfra-csirs-ResourceList CFRA-CSIRS-ResourceList } CFRA-Resource ::=SEQUENCE { ra-PreambleIndex INTEGER (0..XX) } CFRA-SSB-ResourceList ::=SEQUENCE (SIZE(1..maxRAssbResources)OF CFRA-SSB- ResourceCFRA-CSIRS-ResourceList::= SEQUENCE (SIZE(1..maxRAcsirsResources)OFCFRA-CSIRS- Resource CFRA-SSB-Resource::= SEQUENCE { ssb SSB-ID,ra-Resource RA-Resource } CFRA-CSIRS-Resource ::= SEQUENCE { csirsCSIRS-ID, ra-Resource RA-Resource } RA-Resource ::= SEQUENCE {ra-PreambleIndex INTEGER (0..XX), ra-ResourceIndexList SEQUENCE(SIZE(1..##) OF ra-ResourceIndex INTEGER (0..YY) } maxRAssbResourcesINTEGER ::= 64 -- Maximum number of RA resources associated with SSBsmaxRAcsirsResources INTEGER ::= 32 -- Maximum number of RA resourcesassocaited with CSI-RS configurations -- ASN1STOP

For NR, the parameters for the common RACH configuration for the targetcell may be signaled in the handover command using anNR-RACH-ConfigCommon IE such as the one shown below. For scenarios wherethe common RACH configuration is not signaled in the handover command,the common RACH configuration for the target cell may be determinedusing any SI acquisition method defined for NR provided below:

(i) the common RACH configuration for the target cell may be acquired byreading the SI broadcast from the target cell;

(ii) the common RACH configuration for the target cell may be obtainedfrom stored SI that is valid for the target cell;

(iii) if the target cell and source cell are part of the same SI Area,the common RACH configuration for the target cell can be assumed thesame as the common RACH configuration for source cell.

-- ASN1START RACH-ConfigCommon ::= SEQUENCE { cbra-ResourcesCBRA-Resources, powerRampingParameters PowerRampingParameters,ra-SupervisionInfo SEQUENCE { preambleTransMax PreambleTransMax,ra-ResponseWindowSize ENUMERATED { u2, u3, u4, u5, u6, u7, u8, u10},ra-ContentionResolutionTimer ENUMERATED { u8, u16, u24, u32, u40, u48,u56, u64} } } CBRA-Resources ::= SEQUENCE { numberOfRA-PreamblesNumberOfPreambles, preamblesGroupAConfig SEQUENCE {sizeOfRA-PreamblesGroupA NumberOfPreambles, ra-Msg3SizeGroupARA-Msg3Sizes, -- In LTE there is also a power offset for groupB ... }OPTIONAL -- NEED R } NumberOfPreambles ::= ENUMERATED {nX, nY} -- Note:the highest value cannot be used for sizeOfRA-PreamblesGroupARA-Msg3Sizes ::= {bX, bY} PowerRampingParameters ::= SEQUENCE {powerRampingStep ENUMERATED {dbBX, dBY},preambleInitialReceivedTargetPower ENUMERATED {dBm-X, dBm-Y} } --ASN1STOP

FIG. 8 illustrates a model that may be used for PRACH resourceselection. The inputs to the model include the detected beams of thetarget cell and thresholds and selection criterion used to configure thealgorithms. The output of the model is the PRACH resource that is usedto access the target cell.

The PRACH resource selection model is composed of two main functions: asuitability check function and a beam & PRACH resource selectionfunction.

The suitability check function determines which of the detected beams ofthe target cell are suitable for performing random access. Thesuitability of a beam may be based on a quality threshold, where thethreshold may be specified or configured by the network via broadcastand/or dedicated signaling. For embodiments where the threshold isconfigured by the network, the threshold may be signaled in theNR-RACH-ConfigCommon or NR-RACH-ConfigDedicated IEs. Alternatively, thethreshold used for PRACH resource selection could be the same as thethreshold used to perform beam selection for the cell quality derivationthat is performed for cell (re-)selection or RRM measurements. In oneembodiment, the threshold is based on RSRP; i.e. detected beams with acorresponding RSRP measurement that is greater than or equal to thethreshold are considered suitable. Alternatively, the threshold may bebased on RSRQ, SINR, estimated DL or UL data rate(s), CQI or any othermeasurement quantity defined for NR.

The same threshold may be used when determining the suitability of allbeams. Alternatively, separate thresholds may be used, depending on thecharacteristics of the beams. For example, the threshold used for a beammay be dependent on the type of resource associated with the beam,thereby allowing the selection of suitable beams to be biased towardsbeams associated with a specific type of resource. In one embodiment, afirst threshold, e.g., SSB-threshold, may be used for beams associatedwith SS blocks and a second threshold, e.g., CSI-RS threshold, may beused for beams associated with CSI-RS configurations. In anotherembodiment, a 1st threshold may be used for beams associated withdedicated PRACH resources and a second threshold may be used for beamsassociated with common PRACH resources. To determine which threshold touse if a beam is associated with more than one type of resource, a rulemay be specified. For example, if a beam is associated with more thanone type of resource, the threshold with the smallest value can be used.In another example, if a beam is associated with dedicated and commonPRACH resources, the threshold used for beams associated with dedicatedPRACH resource can be used.

In another embodiment, a beam-specific offset is applied whendetermining the suitability of a beam, thereby allowing the selection ofsuitable beams to be biased towards a specific beam or group of beams.For example, the beams that are not preferred may be configured with anoffset that is less that the offset configured for the preferred beams,thereby requiring the quality of the beams that are not preferred to bebetter than the preferred beams in order for them to pass thesuitability check. The beam-specific offset may also be used whenranking the suitable beams, thereby allowing the preferred beams to beranked higher.

In another embodiment, the suitability check function is disabled so thebeam and PRACH resource selection function can be performed on thedetected beams. In the proposed model, this can be accomplished bysetting the suitability threshold(s) to an arbitrarily low value suchthat all detected beams will pass the suitability check.

For scenarios where none of the beams satisfy threshold(s), the PRACHresource selection may be considered not successful and indication ofthe failure to detect a suitable beam may be sent to higher layers.Alternatively, if none of the beams satisfy the threshold(s), the UE mayconsider any beam that allows the UE to meet the target received powerof the RACH preamble with its maximum transmit power as a suitable beam.Yet in another alternative, when no suitable beam is found, the UE mayselect the best beam among the detected beams associated with dedicatedRACH resources if available, or the best beam among the detected beamsassociated with the common RACH resources if available, or simply thebest beam among all detected beams.

Separately, the beam and PRACH resource selection function determineswhich PRACH resource to select from the set of PRACH resourcesassociated with the suitable beams. The selection criterion is used tocontrol how the beam and PRACH resource are selected. The selectioncriterion may be specified and/or configured by the network viabroadcast and/or dedicated signaling. When selecting the PRACH resource,one or more of the following may be considered: (i) the measurementquantity of the beam associated with the PRACH resource, e.g., RSRP,RSRQ, SINR or CQI; (ii) the type of RS associated with the beam; e.g.,SS or CSI-RS; (iii) the type of PRACH resource; e.g., dedicated orcommon; and (iv) the Time/Frequency (T/F) resource used by the PRACHresource. Note: The NR-UNIT containing a PRACH resource may be asubframe, TTI, slot, mini-slot, symbol or any other time unit definedfor NR.

The PRACH resource selection model may be integrated with the RRMmeasurement model as shown in the figures below. FIG. 9 is an embodimentwhere the inputs to the PRACH resource selection model correspond to thebeam measurements after the L3 beam filtering. FIG. 10A is an alternateembodiment where the inputs to the PRACH resource selection modelcorrespond to the beam measurements before the L3 beam filtering. FIG.10B is yet another embodiment where the inputs to the PRACH resourceselection model correspond to the beam measurements after L2 beamfiltering, where the L2 filter may be UE implementation specific orconfigured by the network; e.g. via RRC signaling.

In the following sections, we propose alternate solutions for performingPRACH resource selection based on the model proposed above. By makingsome or all configuration parameters/selection criterion configurablevia the network, the proposed PRACH resource selection functionality canbe optimized for the various deployment scenarios and use cases beingconsidered for NR.

Unless otherwise indicated in the descriptions of the procedures below,if the gNB includes dedicated RACH resources in the handover command,the UE shall attempt to use the dedicated RACH resources first ifcorresponding beam(s) are suitable. If the gNB includes in the handovercommand, downlink beam information (SS based beam or CSI-RS based beam)but no corresponding dedicated RACH resources for any of the downlinkbeam, the UE should perform random access procedure by selecting a RACHresource from the configured common RACH resources.

In the descriptions of the procedures below, the following terms may beused interchangeably: (i) “dedicated PRACH resource(s)” and “contentionfree RA resource(s)”; (ii) “common PRACH resource(s)” and “contentionbased RA resource(s)”; and (iii) “PRACH opportunity” and “PRACHoccasion.”

According to an alternative embodiment, it is envisaged to select thePRACH resource used for access to the target cell from the set of PRACHresources associated with the “best” beam. If the “best” beam isassociated with dedicated and common PRACH resources, the PRACH resourceis selected from the set of dedicated PRACH resources. The NR-UNITcontaining the next available PRACH opportunity may be a subframe, TTI,slot, mini-slot, symbol or any other time unit defined for NR. A flowchart illustrating the steps of the proposed PRACH resource selectionprocedure is shown in FIG. 11. The following steps as disclosed beloware denoted by Arabic numerals.

1. The UE determines which of the detected beams of the target cell aresuitable for performing random access using the methods discussed above.A single threshold may be used to determine the suitability of thedetected beams. The threshold may be set to a value that corresponds tothe minimum quality that is required to use a beam for random access.Multiple threshold may be used, where a given threshold is dependent onthe type of reference signal associated with the beam. For example, afirst threshold; e.g. SSB-threshold, may be used for beams associatedwith SS blocks and a second threshold; e.g. CSI-RS threshold, may beused for beams associated with CSI-RS configurations. If none of thebeams satisfy the threshold(s), the UE may consider any beam that allowsthe UE to meet the target received power of the RACH preamble with itsmaximum transmit power as a suitable beam. Alternatively, when nosuitable beam is found, the UE may select the best beam among thedetected beams associated with dedicated RACH resources if available, orthe best beam among the detected beams associated with the common RACHresources if available, or simply the best beam among all detectedbeams. If a minimum quality is not required, the threshold may be set toan arbitrarily low value such that all detected beams will pass thesuitability check.

2. If there are not any suitable beams, the PRACH resource selection isconsidered not successful and the procedure ends. An indication of thefailure may be sent to higher layers. Alternatively, when no suitablebeam is found, the UE may select the best beam among the detected beamsassociated with dedicated RACH resources if available, or the best beamamong the detected beams associated with the common RACH resources ifavailable, or simply the best beam among all detected beams. Yet inanother alternatively, the UE may continue to perform measurements andrepeat the suitability check multiple times before the PRACH resourceselection is considered not successful. The repetition of the proceduremay be controlled using a counter, thereby allowing the procedure to berepeated up to N times. In another embodiment, the repetition of theprocedure may be controlled using a timer, where the procedure may berepeated until the timer expires. And in yet another embodiment, therepetition of the procedure may be controlled by a counter and a timer,thereby allowing the procedure to be repeated up to N times before thetimer expires.

3. The “best” beam; e.g., the one with the greatest RSRP, is selectedfrom the set of suitable beams.

4. The UE determines if there are dedicated PRACH resources associatedwith the selected beam. The UE may be informed of the associationbetween beams and dedicated PRACH resources using dedicated signaling,e.g., using, the NR-RACH-ConfigDedicated IE signaled via the handovercommand.

5. If the selected beam is associated with dedicated PRACH resources,the UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. Otherwise,the procedure continues with the next step. If the set of dedicatedPRACH resources associated with the beam includes more than onededicated PRACH resource, the UE may select the PRACH resource atrandom. Alternatively, the UE may take the T/F configuration of thededicated PRACH resources into consideration when making the selection.For example, if the beam is associated with multiple PRACH resourcesthat occur at different times, then it may be advantageous for the UE toselect the PRACH resource whose PRACH opportunity occurs next.

6. The UE selects a common PRACH resource from the set of common PRACHresources associated with the beam, the PRACH resource selection isconsidered successful and the procedure ends. If the set of common PRACHresources associated with the beam includes more than one common PRACHresource, the UE may select the beam as described for the case when thePRACH resource is selected from a set that includes more than onededicated PRACH resource; e.g. at random, based on the T/F configurationof the common PRACH resources.

According to an alternative embodiment, a technique is envisaged toselect the PRACH resource used for access to the target cell from theset of PRACH resources associated with the “best” beam, where the “best”beam is first attempted to be selected from the set of suitable beamsassociated with dedicated PRACH resources; and if no such beams exist,the “best” beam is selected from the set of suitable beams associatedwith common PRACH resources. The NR-UNIT containing the next availablePRACH opportunity may be a subframe, TTI, slot, mini-slot, symbol or anyother time unit defined for NR. A flow chart illustrating the steps, asdenoted by Arabic numerals, of the proposed PRACH resource selectionprocedure is shown in FIG. 12.

1. The UE determines which of the detected beams of the target cell aresuitable for performing random access using methods described above. Asingle threshold may be used to determine the suitability of thedetected beams. The threshold may be set to a value that corresponds tothe minimum quality that is required to use a beam for random access.Multiple thresholds may be used, where a given threshold is dependent onthe type of reference signal associated with the beam. For example, a1^(st) threshold; e.g., SSB-threshold, may be used for beams associatedwith SS blocks and a 2^(nd) threshold; e.g. CSI-RS threshold, may beused for beams associated with CSI-RS configurations. If none of thebeams satisfy the threshold(s), the UE may consider any beam that allowsthe UE to meet the target received power of the RACH preamble with itsmaximum transmit power as a suitable beam. Alternatively, when nosuitable beam is found, the UE may select the best beam among thedetected beams associated with dedicated RACH resources if available, orthe best beam among the detected beams associated with the common RACHresources if available, or simply the best beam among all detectedbeams. If a minimum quality is not required, the threshold may be set toan arbitrarily low value such that all detected beams will pass thesuitability check.

2. If there aren't any suitable beams, the PRACH resource selection isconsidered not successful and the procedure ends. An indication of thefailure may be sent to higher layers. Alternatively, when no suitablebeam is found, the UE may select the best beam among the detected beamsassociated with dedicated RACH resources if available, or the best beamamong the detected beams associated with the common RACH resources ifavailable, or simply the best beam among all detected beams. Yet inanother alternative, the UE may continue to perform measurements andrepeat the suitability check multiple times before the PRACH resourceselection is considered not successful. The repetition of the proceduremay be controlled using a counter, thereby allowing the procedure to berepeated up to N times. In another embodiment, the repetition of theprocedure may be controlled using a timer, where the procedure may berepeated until the timer expires. And in yet another embodiment, therepetition of the procedure may be controlled by a counter and a timer,thereby allowing the procedure to be repeated up to N times before thetimer expires.

3. The UE determines if there are dedicated PRACH resources associatedwith the set of suitable beams. The UE may be informed of theassociation between beams and dedicated PRACH resources using dedicatedsignaling, e.g., using the NR-RACH-ConfigDedicated IE signaled via thehandover command.

4. If there are suitable beams associated with dedicated PRACHresources, the “best” beam, e.g., the one with the greatest RSRP, isselected from the set of suitable beams associated with dedicated PRACHresources and the procedure continues with the next step. Otherwise, thenext step is skipped.

5. The UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. If the set ofdedicated PRACH resources associated with the beam includes more thanone dedicated PRACH resource, the UE may select the PRACH resource atrandom. Alternatively, the UE may take the T/F configuration of thededicated PRACH resources into consideration when making the selection.For example, if the beam is associated with multiple PRACH resourcesthat occur at different times, then it may be advantageous for the UE toselect the PRACH resource whose PRACH opportunity occurs next.

6. The UE selects a common PRACH resource from the set of common PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. If the set ofcommon PRACH resources associated with the beam includes more than onecommon PRACH resource, the UE may select the beam as described for thecase when the PRACH resource is selected from a set that includes morethan one dedicated PRACH resource; e.g. at random, based on the T/Fconfiguration of the common PRACH resources.

According to yet even a further alternative embodiment, it is envisagedto select the PRACH resource used for access to the target cell from theset of PRACH resources associated with the suitable beam whose PRACHopportunity occurs next. If the beam is associated with dedicated andcommon PRACH resources, the PRACH resource is selected from the set ofdedicated PRACH resources. The NR-UNIT containing the next availablePRACH opportunity may be a subframe, TTI, slot, mini-slot, symbol or anyother time unit defined for NR. A flow chart illustrating the steps, asdenoted by Arabic numerals, of the proposed PRACH resource selectionprocedure is shown in FIG. 13.

1. The UE determines which of the detected beams of the target cell aresuitable for performing random access using the methods described above.For example, a single threshold may be used to determine the suitabilityof the detected beams. The threshold may be set to a value thatcorresponds to the minimum quality that is required to use a beam forrandom access. Multiple thresholds may be used, where a given thresholdis dependent on the type of reference signal associated with the beam.For example, a 1^(st) threshold; e.g. SSB-threshold, may be used forbeams associated with SS blocks and a 2^(nd) threshold; e.g. CSI-RSthreshold, may be used for beams associated with CSI-RS configurations.If none of the beams satisfy the threshold(s), the UE may consider anybeam that allows the UE to meet the target received power of the RACHpreamble with its maximum transmit power as a suitable beam.Alternatively, when no suitable beam is found, the UE may select thebest beam among the detected beams associated with dedicated RACHresources if available, or the best beam among the detected beamsassociated with the common RACH resources if available, or simply thebest beam among all detected beams. If a minimum quality is notrequired, the threshold may be set to an arbitrarily low value such thatall detected beams will pass the suitability check.

2. If there aren't any suitable beams, the PRACH resource selection isconsidered not successful and the procedure ends. An indication of thefailure may be sent to higher layers. Alternatively, when no suitablebeam is found, the UE may select the best beam among the detected beamsassociated with dedicated RACH resources if available, or the best beamamong the detected beams associated with the common RACH resources ifavailable, or simply the best beam among all detected beams. Yet inanother alternatively, the UE may continue to perform measurements andrepeat the suitability check multiple times before the PRACH resourceselection is considered not successful. The repetition of the proceduremay be controlled using a counter, thereby allowing the procedure to berepeated up to N times. In another embodiment, the repetition of theprocedure may be controlled using a timer, where the procedure may berepeated until the timer expires. And in yet another embodiment, therepetition of the procedure may be controlled by a counter and a timer,thereby allowing the procedure to be repeated up to N times before thetimer expires.

3. The UE selects the beam associated with PRACH resources thatcorrespond to the next PRACH opportunity. In one embodiment, if thereare multiple suitable beams associated with the next PRACH opportunity,the UE may select the beam using any method that results in theselection of one of the suitable beams associated with the next PRACHopportunity. For example, the UE may select the beam associated withdedicated PRACH resources, the UE may select the “best” beam; e.g. thebeam with greatest RSRP or the UE may randomly select, with equalprobability, one beam from the set suitable beams associated with thenext PRACH opportunity.

4. The UE determines if there are dedicated PRACH resources associatedwith the selected beam. The UE may be informed of the associationbetween beams and dedicated PRACH resources using dedicated signaling,e.g., using, the NR-RACH-ConfigDedicated IE signaled via the handovercommand.

5. If the selected beam is associated with dedicated PRACH resources,the UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. Otherwise,the procedure continues with the next step. If the set of dedicatedPRACH resources associated with the beam includes more than onededicated PRACH resource, the UE selects the PRACH resource whose PRACHopportunity occurs next.

6. The UE selects a common PRACH resource from the set of common PRACHresources associated with the beam, the PRACH resource selection isconsidered successful and the procedure ends. If the set of common PRACHresources associated with the beam includes more than one common PRACHresource, the UE selects the PRACH resource whose PRACH opportunityoccurs next. If multiple common PRACH resources are configured for thenext PRACH opportunity associated with the beam, the UE may randomlyselect, with equal probability, one PRACH from the set of common PRACHresources configured for the next PRACH opportunity.

According to even a further alternative embodiment, it is envisaged toselect the PRACH resource used for access to the target cell from theset of PRACH resources associated with the suitable beam whose PRACHopportunity occurs next, where the beam is first attempted to beselected from the set of suitable beams associated with dedicated PRACHresources; and if no such beams exist, the beam is selected from the setof suitable beams associated with common PRACH resources. The NR-UNITcontaining the next available PRACH opportunity may be a subframe, TTI,slot, mini-slot, symbol or any other time unit defined for NR. A flowchart illustrating the steps, as denoted by Arabic numerals, of theproposed PRACH resource selection procedure is shown in FIG. 14.

1. The UE determines which of the detected beams of the target cell aresuitable for performing random access using the methods described above.For example, a single threshold may be used to determine the suitabilityof the detected beams. The threshold may be set to a value thatcorresponds to the minimum quality that is required to use a beam forrandom access. Multiple thresholds may be used, where a given thresholdis dependent on the type of reference signal associated with the beam.For example, a 1^(st) threshold; e.g. SSB-threshold, may be used forbeams associated with SS blocks and a 2^(nd) threshold; e.g. CSI-RSthreshold, may be used for beams associated with CSI-RS configurations.If none of the beams satisfy the threshold(s), the UE may consider anybeam that allows the UE to meet the target received power of the RACHpreamble with its maximum transmit power as a suitable beam.Alternatively, when no suitable beam is found, the UE may select thebest beam among the detected beams associated with dedicated RACHresources if available, or the best beam among the detected beamsassociated with the common RACH resources if available, or simply thebest beam among all detected beams. If a minimum quality is notrequired, the threshold(s) may be set to an arbitrarily low value suchthat all detected beams will pass the suitability check.

2. If there aren't any suitable beams, the PRACH resource selection isconsidered not successful and the procedure ends. An indication of thefailure may be sent to higher layers. Alternatively, when no suitablebeam is found, the UE may select the best beam among the detected beamsassociated with dedicated RACH resources if available, or the best beamamong the detected beams associated with the common RACH resources ifavailable, or simply the best beam among all detected beams. Yet inanother alternatively, the UE may continue to perform measurements andrepeat the suitability check multiple times before the PRACH resourceselection is considered not successful. The repetition of the proceduremay be controlled using a counter, thereby allowing the procedure to berepeated up to N times. In another embodiment, the repetition of theprocedure may be controlled using a timer, where the procedure may berepeated until the timer expires. And in yet another embodiment, therepetition of the procedure may be controlled by a counter and a timer,thereby allowing the procedure to be repeated up to N times before thetimer expires

3. The UE determines if there are dedicated PRACH resources usingdedicated signaling, e.g., using associated with the set of suitablebeams. The UE may be informed of the association between beams anddedicated PRACH resources using the NR-RACH-ConfigDedicated IE signaledvia the handover command.

4. If there are suitable beams associated with dedicated PRACHresources, the beam associated with PRACH resources that correspond tothe next PRACH opportunity is selected from the set of suitable beamsassociated with dedicated PRACH resources and the procedure continueswith the next step. If there are not any dedicated PRACH resourcesassociated with the set of suitable beams, the next step is skipped.

In an embodiment, if there are multiple suitable beams associated withthe next PRACH opportunity, the UE may select the beam using any methodthat results in the selection of one of the suitable beams associatedwith the next PRACH opportunity. For example, the UE may select the“best” beam; e.g., the beam with greatest RSRP, or the UE may randomlyselect, with equal probability, one beam from the set suitable beamsassociated with the next PRACH opportunity.

5. The UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. If the set ofdedicated PRACH resources associated with the beam includes more thanone dedicated PRACH resource, the UE selects the PRACH resource whosePRACH opportunity occurs next.

6. The beam associated with PRACH resources that correspond to the nextPRACH opportunity is selected from the set of suitable beams associatedwith common PRACH resources. In one embodiment, if there are multiplesuitable beams associated with the next PRACH opportunity, the UE mayselect the beam using any method that results in the selection of one ofthe suitable beams associated with the next PRACH opportunity. Forexample, the UE may select the “best” beam; e.g., the beam with greatestRSRP, or the UE may randomly select, with equal probability, one beamfrom the set suitable beams associated with the next PRACH opportunity.

7. The UE selects a common PRACH resource from the set of common PRACHresources associated with the beam, the PRACH resource selection isconsidered successful and the procedure ends. If the set of common PRACHresources associated with the beam includes more than one common PRACHresource, the UE selects the PRACH resource whose PRACH opportunityoccurs next. If multiple common PRACH resources are configured for thenext PRACH opportunity associated with the beam, the UE may randomlyselect, with equal probability, one PRACH from the set of common PRACHresources configured for the next PRACH opportunity.

According to yet even a further embodiment, as exemplary illustrated inFIG. 15, an NR deployment describes where SS block transmissions (SSBs)are associated with wide beams and CSI-RS transmissions are associatedwith narrow beams. The narrow beams may be used for high data rateservices. For such a deployment, when performing handover to a targetcell, it would be advantageous to handover to a narrow beam to minimizethe interruption time to the high data rate services. However, sincehandover to a narrow beam may be less reliable than handover to a widebeam, we propose that the handover command includes a first set of PRACHresources associated with the narrow beam(s) that may be used for afirst access attempt and second set of PRACH resources associated withthe wide beam(s) that may be used for a second access attempt in theevent the first access attempt is not successful. In one embodiment, thefirst set of PRACH resources are dedicated PRACH resources associatedwith CSI-RS configurations; i.e. the narrow beams, and the second set ofPRACH resources are common PRACH resources associated with SSBs; i.e.the wide beams. Alternatively, both the first and second set of PRACHresources may be dedicated PRACH resources; i.e. the first set of PRACHresources may be dedicated PRACH resources associated with CSI-RSconfigurations and the second set of PRACH resources may be dedicatedPRACH resources associated with SSBs.

It is noted that for NR, the parameters for the common RACHconfiguration for the target cell may be optionally signaled in thehandover command. Therefore, for scenarios where the second set of PRACHresources are common PRACH resources, the second set of PRACH resourcesmay not be included in the handover command, but may instead bedetermined using an alternate SI acquisition method as described above.

The number of access attempt(s) using the first set of PRACH resourcesmay be controlled using a counter, thereby allowing the UE to perform upto N access attempts using the first set of PRACH resources beforeattempting to access the cell using the second set of PRACH resources.In another embodiment, the number of access attempts using the first setof PRACH resources may be controlled using a timer, thereby allowing theUE to perform multiple access attempts using the first set of PRACHresources until the timer expires. And in yet another embodiment, theaccess attempts using the first set of PRACH resources may be controlledusing a counter and a timer, thereby allowing the UE to perform up to Naccess attempts using the first set of PRACH resources before the timerexpires.

The deployment shown in FIG. 15 is used to illustrate how the proposedsolutions may be used when the SSBs are associated with wide beams andthe CSI-RS configurations are associated with narrow beams. However, theproposed solutions may be used for any scenario that requires “fallback”to a second set of PRACH resources in the event the access attempt(s)using the first set of PRACH resources is not successful. For example,the proposed solutions may also be used when the first set of PRACHresources are dedicated PRACH resources associated with SSBs and thesecond set of PRACH resources are common PRACH resources that are alsoassociated with SSBs.

A flow chart illustrating the steps, as denoted by Arabic numerals, ofthe proposed PRACH resource selection procedure is shown in FIG. 16A.

1. The UE determines which of the detected beams of the target cell aresuitable for performing random access according to methods describedabove. For example, a single threshold may be used to determine thesuitability of the detected beams. The threshold may be set to a valuethat corresponds to the minimum quality that is required to use a beamfor random access. Multiple thresholds may be used, where a giventhreshold is dependent on the type of reference signal associated withthe beam. For example, a first threshold, e.g., SSB-threshold, may beused for beams associated with SS blocks and a second threshold, e.g.,CSI-RS threshold, may be used for beams associated with CSI-RSconfigurations. If none of the beams satisfy the threshold(s), the UEmay consider any beam that allows the UE to meet the target receivedpower of the RACH preamble with its maximum transmit power as a suitablebeam. Alternatively, when no suitable beam is found, the UE may selectthe best beam among the detected beams associated with dedicated RACHresources if available, or the best beam among the detected beamsassociated with the common RACH resources if available, or simply thebest beam among all detected beams. If a minimum quality is notrequired, the threshold may be set to an arbitrarily low value such thatall detected beams will pass the suitability check.

2. If this is the first access attempt, the procedure continues with thenext step. Otherwise the procedure continues with step 8.

3. If there are suitable beams associated with the first set of PRAHresources, e.g., CSI-RS configurations, the procedure continues with thenext step. Otherwise, the procedure continues with the step 8.

4. The “best” beam; i.e., the one with the greatest RSRP, is selectedfrom the set of suitable beams associated with the first set of PRACHresources; e.g., the set of suitable beams associated with CSI-RSconfigurations. Alternatively, the beam associated with PRACH resourcesthat correspond to the next PRACH opportunity may be selected from theset of suitable beams associated with the first set of PRACH resources.

5. The UE determines if there are dedicated PRACH resources associatedwith the selected beam. The UE may be informed of the associationbetween beams and dedicated PRACH resources using dedicated signaling,e.g., using the NR-RACH-ConfigDedicated IE signaled via the handovercommand.

6. If the selected beam is associated with dedicated PRACH resources,the UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. Otherwise,the procedure continues with the next step. If the set of dedicatedPRACH resources associated with the beam includes more than onededicated PRACH resource, the UE may select the PRACH resource atrandom. Alternatively, the UE may take the T/F configuration of thededicated PRACH resources into consideration when making the selection.For example, if the beam is associated with multiple PRACH resourcesthat occur at different times, then it may be advantageous for the UE toselect the PRACH resource whose PRACH opportunity occurs next.

7. The UE selects a common PRACH resource from the set of common PRACHresources associated with the beam, the PRACH resource selection isconsidered successful and the procedure ends. If the set of common PRACHresources associated with the beam includes more than one common PRACHresource, the UE may select the beam as described for the case when thePRACH resource is selected from a set that includes more than onededicated PRACH resource; e.g. at random, based on the T/F configurationof the common PRACH resources.

8. If there are not any suitable beams associated with the second set ofPRACH resources, e.g., SS blocks (SSBs), the PRACH resource selection isconsidered not successful and the procedure ends. An indication of thefailure may be sent to higher layers. Otherwise, the procedure continueswith the next step.

9. The “best” beam; i.e., the one with the greatest RSRP, is selectedfrom the set of suitable beams associated with the second set of PRACHresources; e.g., the set of suitable beams associated with SS blocks.Alternatively, the beam associated with PRACH resources that correspondto the next PRACH opportunity may be selected from the set of suitablebeams associated with the second set of PRACH resources.

10. The UE determines if there are dedicated PRACH resources associatedwith the selected beam. The UE may be informed of the associationbetween beams and dedicated PRACH resources using theNR-RACH-ConfigDedicated IE signaled via the handover command.

11. If the selected beam is associated with dedicated PRACH resources,the UE selects a PRACH resource from the set of dedicated PRACHresources associated with the selected beam, the PRACH resourceselection is considered successful and the procedure ends. Otherwise,the procedure continues with the next step. If the set of dedicatedPRACH resources associated with the beam includes more than onededicated PRACH resource, the UE may select the PRACH resource atrandom. Alternatively, the UE may take the T/F configuration of thededicated PRACH resources into consideration when making the selection.For example, if the beam is associated with multiple PRACH resourcesthat occur at different times, then it may be advantageous for the UE toselect the PRACH resource whose PRACH opportunity occurs next.

12. The UE selects a common PRACH resource from the set of common PRACHresources associated with the beam, the PRACH resource selection isconsidered successful and the procedure ends. If the set of common PRACHresources associated with the beam includes more than one common PRACHresource, the UE may select the beam as described for the case when thePRACH resource is selected from a set that includes more than onededicated PRACH resource; e.g. at random, based on the T/F configurationof the common PRACH resources.

According to yet even a further embodiment, it is assumed the beam usedfor initial access on the downlink is SS based beam. The gNB may includein the handover command, an SS based beam and/or the corresponding SSblock. For each beam or SS block included in the handover command forinitial access, the gNB assigns only one dedicated RACH resource. ThegNB may include more than one beam and/or SS block in the handovercommand. The UE may select the beam/SS Block and the corresponding RACHresource to use for initial access using one of the beam selectionprocedures described above.

In another embodiment, the gNB may include in the handover command, anindication to use more than one RACH resources for parallel initialattempts for e.g., using this indication, the UE may transmit one ormore additional RACH preambles before the RAR of the first transmittedpreamble. Furthermore, the gNB may also include in the handover command,how many parallel attempts, the UE may be allowed to perform. For eachbeam or SS block included in the handover command for initial access,the gNB may assign more than one dedicated RACH resource. The UE maydetermine RACH resources for parallel initial attempts, by selecting theup to the number of corresponding beams/SS blocks using one of the beamselection procedures described above. In an alternative embodiment, theUE may selects the beams for initial attempt as the highest ranked beamswhere the beams are ranked in decreasing order of the number of thecorresponding CSI-RS beams with quality above a configured threshold.

In this embodiment, it is assumed the beam used for initial access onthe downlink is CSI-RS based beam. The gNB may include in the handovercommand, a CSI-RS based beam and/or the corresponding CSI-RS resource.For each beam or CSI-RS resource included in the handover command forinitial access, the gNB assigns only one dedicated RACH resource. ThegNB may include more than one beam and/or CSI-RS resource in thehandover command. The UE may select the beam/CSI-RS resource and thecorresponding RACH resource to use for initial access using one of thebeam selection procedures described above.

In another embodiment, the gNB may include in the handover command, anindication to use more than one RACH resources for parallel initialattempts for e.g. using this indication, the UE may transmit one or moreadditional RACH preambles before the RAR of the first transmittedpreamble. Furthermore, the gNB may also include in the handover command,how many parallel attempts, the UE may be allowed to perform. For eachbeam or CSI resource included in the handover command for initialaccess, the gNB may assigns more than one dedicated RACH resource. TheUE may determine RACH resources for parallel initial attempts, byselecting the up to the number of corresponding beams/CSI-RS resourceusing one of the beam selection procedures described above.

The UE may also provide assistance information for the UL beamselection. For e.g., the UE may transmit periodic UL reference signalfor e.g. an UL reference signal in support of the UL measurementmobility based solution being considered for 5G. The target cell mayinclude in the RRC reconfiguration message passed to the source cell forinclusion in the handover command, the UL beam to be used for theinitial access procedure, e.g., for each RACH resource (dedicated RACHresource or common RACH resource), the handover command may include theUL beam that the UE should use.

According to yet another embodiment, it is envisaged to select the PRACHresource used for access to the target cell from the set of PRACHresources associated with a selected beam. A condition may be based onthe number of random access re-transmissions, the expiration of a timer,the notification of power ramping suspension from lower layers or anycombination thereof. It may be used to determine if the beam should beattempted to be selected from the set of beams associated with dedicatedPRACH resources or if the beam should be attempted to be selected fromthe set of beams associated with common PRACH resources, i.e., when theUE should “fallback” to the common PRACH resources. A flow chartillustrating the steps of the proposed PRACH resource selectionprocedure is shown in FIG. 16B. The steps of the proposed PRACH ResourceSelection procedure are performed as follows:

1. Determine which of the detected beams of the target cell are suitablefor performing random access using the methods described above. Forexample, a threshold may be used to determine the suitability of thedetected beams. The threshold may be set to a value that corresponds tothe minimum quality that is required to use a beam for random access.Alternatively, multiple thresholds may be used, where a given thresholdis dependent on the type of reference signal associated with the beam.For example, a first threshold; e.g., SSB-threshold, may be used forbeams associated with SS blocks and a second threshold; e.g., CSI-RSthreshold, may be used for beams associated with CSI-RS configurations.If none of the beams satisfy the threshold(s), any beam that allows theUE to meet the target received power of the RACH preamble with itsmaximum transmit power may be considered as a suitable beam.Alternatively, when no suitable beam is found, the UE may select thebest beam among the detected beams associated with dedicated RACHresources if available, or the best beam among the detected beamsassociated with the common RACH resources if available, or simply thebest beam among all detected beams. Alternatively, if a minimum qualityis not required, the threshold(s) may be set to an arbitrarily low valuesuch that all detected beams will pass the suitability check.

If no suitable beams exist, one approach is to consider the PRACHResource Selection procedure as being unsuccessfully completed. Inanother approach, the UE may continue to perform measurements and repeatthe suitability check multiple times before the PRACH resource selectionis considered not successful. The repetition of the procedure may becontrolled using a counter, thereby allowing the procedure to berepeated up to N times. In another embodiment, the repetition of theprocedure may be controlled using a timer, where the procedure may berepeated until the timer expires. And in yet another embodiment, therepetition of the procedure may be controlled by a counter and a timer,thereby allowing the procedure to be repeated up to N times before thetimer expires. In yet another alternative, when no suitable beam isfound, the UE may select the best beam among the detected beamsassociated with dedicated RACH resources if available, or the best beamamong the detected beams associated with the common RACH resources ifavailable, or simply the best beam among all detected beams.

According to another embodiment, if the condition is to “fallback” tothe common PRACH resources was met, then (i) if there are one or moresuitable beams associated with common PRACH resources: (a) select a beamfrom the set of suitable beams associated with common PRACH resources;(1) if there is only one suitable beam associated with common PRACHresources, select that beam; or (2) if there are multiple suitable beamsassociated with common PRACH resources: (A) select the beam using anymethod that results in the selection of one of the suitable beamsassociated with common PRACH resources. For example, the UE may selectthe beam associated with common PRACH resources that corresponds to thenext PRACH opportunity. Alternatively, the UE may select the “best”beam; e.g., the beam with greatest RSRP, or the UE may randomly select,with equal probability, a beam from the set suitable beams associatedwith common PRACH resources.

If the condition is to “fallback” to the common PRACH resources was met,then (b) select a common PRACH resource associated with the selectedbeam: (1) if there is only one common PRACH resource associated with theselected beam, select that common PRACH resource; or (2) if there aremultiple common PRACH resources associated with the selected beam: (A)select the common PRACH resource using any method that results in theselection of one of the common PRACH resources associated with theselected beam. For example, the UE may select the common PRACH resourcewhose PRACH opportunity occurs next or the UE may randomly select, withequal probability, one common PRACH resource from the set of commonPRACH resources associated with the selected beam.

The approach may be to (c) consider the PRACH Resource Selectionprocedure successfully completed. In addition, in (d) we consider thePRACH Resource Selection procedure unsuccessfully completed.

According to another embodiment and/or in furtherance of embodimentsdiscussed above, (ii) if there are one or more suitable beams associatedwith dedicated PRACH resources: (a) select a beam from the set ofsuitable beams associated with dedicated resources: (1) if there is onlyone suitable beam associated with dedicated PRACH resources, select thatbeam; or (2) if there are multiple suitable beams associated withdedicated PRACH resources:

(A) select the beam using any method that results in the selection ofone of the suitable beams associated with dedicated PRACH resources. Forexample, the UE may select the beam associated with dedicated PRACHresources that correspond to the next PRACH opportunity. The UE mayselect the “best” beam; e.g., the beam with greatest RSRP, or the UE mayrandomly select, with equal probability, one beam from the set suitablebeams associated with dedicated PRACH resources.

In (b), select a dedicated PRACH resource associated with the selectedbeam, if (1) if there is only one dedicated PRACH resource associatedwith the selected beam, select that dedicated PRACH resource; or (2) ifthere are multiple dedicated PRACH resources associated with theselected beam: (A) select the dedicated PRACH resource using any methodthat results in the selection of one of the dedicated PRACH resourcesassociated with the selected beam. For example, the UE may select thededicated PRACH resource whose PRACH opportunity occurs next or the UEmay randomly select, with equal probability, one dedicated PRACHresource from the set of common PRACH resources associated with theselected beam.

In (c) consider the PRACH Resource Selection procedure successfullycompleted. In (d) consider the PRACH Resource Selection procedureunsuccessfully completed.

According to yet even a further embodiment, it is envisaged to selectthe PRACH resource used for accessing the target cell from the set ofPRACH resources associated with a suitable beam. The beam is initiallyattempted to be selected from the set of suitable beams associated withcontention free RA resources (a.k.a. dedicated PRACH resources); and ifno such beams exist, the beam is selected from the set of suitable beamsassociated with common PRACH resources. In one embodiment, a beam isrepresented by a beam index. For example, beams associated with NR-SS isidentified using the SSB index, and beams associated CSI-RS may beidentified using the CSI-RS configuration index. The NR-UNIT containingthe next available PRACH opportunity (a.k.a. PRACH occasion) may be asubframe, TTI, slot, mini-slot, symbol or any other time unit definedfor NR.

An exemplary illustration of the steps of this proposed PRACH resourceselection procedure at the UE is depicted in FIG. 16C. In the firstquery box of the illustrated decision tree, it is determined whether alist of contention free RA resources has been explicitly provided byRRC. If the answer is Yes, the next query is (i) whether the list ofcontention free RA resources contains a list of SSB indices. If Yes, (a)a suitable SSB index is selected from the set of explicitly provided SSBindices. The SSB index is considered suitable if it corresponds to a SSBwhose quality is above ssb-Threshold. If No, (b) a query is made whetherthe list of CFRA contains CSI-RS indices. If CSI-RS indices areavailable (Yes), (1) a suitable CSI-RS index is selected from the set ofexplicitly provided CSI-RS indices. A CSI-RS index is consideredsuitable if it corresponds to a CSI-RS whose quality is abovecsi-rs-Threshold. If the suitable index is selected from either stepabove—(i)(a) or (i)(b)(1)—the PREAMBLE_INDEX is set to thera-PreambleIndex corresponding to the selected index.

If the answer to the initial query (i) of whether a list of contentionfree RA resources has been explicitly provided is No, or alternativelyif there is no list containing CSI-RS indices, or alternatively if thereis no suitable index selected, then the next query is (ii) whether thefirst Msg3 has not yet been transmitted (i.e., first Msg3 transmission).If the answer to (ii) is yes, (a) a suitable SSB index is selected fromthe set of common SSB indices. An SSB index is considered suitable if itcorresponds to a SSB whose quality is above ssb-Threshold. Next, if both(1) the Random Access Preambles group B exists on the selected SSB, and(2) the potential Msg3 size (UL data available for transmission plus MACheader and, where required, MAC CEs) is greater than ra-Msg3SizeGroupAon the selected SSB, then (A) Random Access Preambles group B isselected. Otherwise, if (1) and (2) are both false, then (B) RandomAccess Preambles group A is selected.

In a further embodiment, if the answer to query (ii), namely whether thefirst Msg3 has not yet been transmitted, is No, then (b) selection ismade of the same SSB index as was used for the preamble transmissionattempt corresponding to the first transmission of Msg3.

In an alternative embodiment when the answer to (ii) is No, step (b)selects the same SSB index used for the preamble transmission attemptcorresponding to the first transmission of Msg3 if suitable. Otherwise,one suitable SSB index from the set of common SSB indices is selectedwhere an SSB index is suitable if it corresponds to a SSB whose qualityis above ssb-Threshold.

In yet another alternative embodiment when the answer to (ii) is No,then (c) select an SSB index from the set of explicitly provided SSBindices whose quality is above the quality of the SSB index used for thepreamble transmission attempt. This corresponds to the firsttransmission of Msg3 plus a hysteresis parameter. If no such SSB indexexists, select the same SSB index as was used for the preambletransmission attempt corresponding to the first transmission of Msg3 ifit is suitable. Otherwise, select one suitable SSB index from the set ofcommon SSB indices, where an SSB index is considered suitable if it iscorresponding to a SSB whose quality is above ssb-Threshold.

According to a further embodiment, and subsequent to query step (ii)(b)discussed above, a selection (1) can be made of the same group of RandomAccess Preambles used for the preamble transmission attemptcorresponding to the first transmission of Msg3. Alternatively, if thesame SSB index used for the preamble transmission attempt correspondingto the first transmission of Msg3 was selected in the previous step,then in step (A) select the same group of Random Access Preambles as wasused for the preamble transmission attempt corresponding to the firsttransmission of Msg3. Otherwise, in step (B), if the potential Msg3 size(UL data available for transmission plus MAC header and, where required,MAC CEs) is greater than ra-Msg3SizeGroupA on the selected SSB, selectthe Random Access Preambles group B. Otherwise select the Random AccessPreambles group A.

According to a further embodiment, and subsequent to step (ii)(a) or(ii)(b) discussed above, in step (c) a ra-PreambleIndex within theselected group randomly with equal probability is selected. Thereafterin step (d) the PREAMBLE_INDEX to the selected ra-PreambleIndex is set;Thereafter in step (e), the next available PRACH occasion is determined.Further in step (f), the Random Access Preamble transmission procedureis performed.

Load Balancing Between Beams of the Target Cell

According to another aspect, a technique is envisaged to perform loadbalancing between the beams of the target cell when performing randomaccess. As shown in FIG. 17, a signaling procedure that may be used toperform load balancing between the beams of the target cell whenperforming random access is described. Each of the steps of FIG. 17 isdenoted by an Arabic numeral.

1. The source gNB configures the UE measurement procedures and the UEreports according to the measurement configuration.

2. The source gNB decides to handover the UE, based on measurementreports and RRM information, and issues a Handover Request over the Xninterface.

3. The target gNB performs admission control and provides the RRCconfiguration as part of the Handover Acknowledgement message.

4. The source gNB provides the RRC configuration to the UE in theHandover Command message. The Handover Command message includes at leastcell ID and all information required to access the target cell so thatthe UE can access the target cell without reading system information.For some cases, the information required for contention based andcontention free random access can be included in the Handover Commandmessage. The access information to the target cell may include beamspecific information, if any.

5. The UE performs PRACH resource selection and transmits the RandomAccess Preamble (RAP) using the selected resource.

6. The target gNB determines the load on the beam used by the UE toaccess the cell is overloaded and directs the UE to use a differentbeam. The target gNB may decide which beam to direct the UE based oninformation provided in the Handover Request message. The MAC RAR shownin FIG. 18 may be used to direct the UE to use a different beam duringthe random access procedure. In one embodiment, the Beam Switch Commandfield is optionally included in the RAR. Whether or not the field isincluded in the RAR may by indicated via the Type field in the MACheader for the RAR; i.e. the Type field may include an additional bit toindicate the presence or absence of the Beam Switch command field. Inone embodiment, the Beam Switch Command is comprised of a bit toindicate if the beam to switch to is associated with an SS block or aCSI-RS configuration and multiple bits to indicate the ID of the beam;e.g. SS block ID, CSI-RS configuration ID.

7. The UE moves the RRC connection to the target gNB and replies withthe Handover Complete message using the beam indicated in the RAR.

Prioritized Random Access

According to yet a further aspect of the application, techniques areproposed to perform prioritized random access. For NR, it has beenagreed that random access will be performed for at least the followingevents: (i) Initial access from RRC_IDLE; (ii) RRC ConnectionRe-establishment procedure; (iii) Handover; (iv) DL data arrival duringRRC_CONNECTED requiring random access procedure, e.g. when ULsynchronisation status is “non-synchronised”; (v) UL data arrival duringRRC_CONNECTED requiring random access procedure, e.g. when ULsynchronisation status is “non-synchronised” or there are no PUCCHresources for SR available; and (vi) Transition from RRC_INACTIVE toRRC_CONNECTED.

To provide differentiation when performing random access, it isenvisaged that one or more of following parameters may be configuredwith values that are dependent on the random access priority:

1. powerRampingStep: power ramping step used for preambleretransmissions;

2. initial back off parameter: default back off time used for preambleretransmissions when the RAR does not contain a Backoff Indicator (BI);

3. Backoff Multiplier: scale factor used to adjust the back offparameter when the RAR contains a BI; and

4. Maximum # of Msg3 HARQ retransmissions.

The values for these parameters may be signaled to the UEs via broadcastor dedicated signaling. For example, the SI broadcast by the gNB mayinclude multiple sets of values, where each set of parameterscorresponds to a different random access priority. Alternatively,dedicated RRC signaling may be used to configure UE specific values foreach set parameters.

When a random access procedure is triggered for events such as initialaccess, RRC connection re-establishment, UL data arrival or transitionfrom RRC_INACTIVE to RRC_CONNECTED, a CBRA procedure may be performed.For such scenarios, it is envisaged that the priority of the randomaccess procedure is based on a set of rules that are specified, wherethe priority of the random access procedure may be determined from theUE's access class, the event type, the QCI of the data triggering therandom access procedure or any combination thereof.

When a random access procedure is triggered for events such as handoverand DL data arrival a CFRA procedure may be performed. For suchscenarios, we propose that in addition to dedicated random accessresource(s), the gNB also indicates the priority of the random accessprocedure. For example, the handover command may include an additionalfield to signal the random access priority; e.g. as high or low. And inthe case of DL data arrival, the gNB may use an NR-PDCCH order thatincludes an additional bit to signal the random access priority; e.g. ashigh or low. Alternatively, the priority of such events could bespecified. For example, when performing CFRA, there will not becontention, so it is unlikely that a retransmission will be required.Therefore, the random access priority when performing CFRA could beconsidered low.

It also possible to perform a CBRA procedure for events such as handoverand DL data arrival. For such scenarios, we propose that the priority ofthe random access procedure is based on a set of rules that arespecified, where the priority of the random access procedure may bedetermined from the UE's access class, the event type, the QCI of thedata triggering the random access procedure or any combination thereof.

According to the present application, it is understood that any or allof the systems, methods and processes described herein may be embodiedin the form of computer executable instructions, e.g., program code,stored on a computer-readable storage medium which instructions, whenexecuted by a machine, such as a computer, server, M2M terminal device,M2M gateway device, transit device or the like, perform and/or implementthe systems, methods and processes described herein. Specifically, anyof the steps, operations or functions described above may be implementedin the form of such computer executable instructions. Computer readablestorage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information, but such computer readable storage media do not includesignals. Computer readable storage media include, but are not limitedto, RAM, ROM, EEPROM, flash memory or other memory technology, CD ROM,digital versatile disks (DVD) or other optical disk storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other physical medium which can be used to storethe desired information and which can be accessed by a computer.

According to yet another aspect of the application, a non-transitorycomputer-readable or executable storage medium for storingcomputer-readable or executable instructions is disclosed. The mediummay include one or more computer-executable instructions such asdisclosed above in the plural call flows according to FIGS. 11-14, 16A-Cand 17. The computer executable instructions may be stored in a memoryand executed by a processor disclosed above in FIGS. 1C and 1F, andemployed in devices including a node such as for example, a base stationand end-user equipment. In particular, the UE as shown for example inFIGS. 1B and 1E is configured to perform the instructions of detectingbeams associated with a target cell. The processor is also configured toexecute the instruction of determining, via a check function, which ofthe detected beams meet a quality threshold for performing randomaccess. The processor is also configured to execute the instructions ofreceiving, at a resource selection function, the threshold-meetingdetected beams. Further, the processor is configured to execute theinstructions of selecting, PRACH resources associated from thethreshold-meeting detected beams. In another embodiment, the processormay also be configured to perform the instructions of load balancingbetween beams of a target cell during random access.

While the systems and methods have been described in terms of what arepresently considered to be specific aspects, the application need not belimited to the disclosed aspects. It is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the claims, the scope of which should be accorded the broadestinterpretation so as to encompass all such modifications and similarstructures. The present disclosure includes any and all aspects of thefollowing claims.

What is claimed is:
 1. An apparatus in a network comprising: anon-transitory memory including instructions stored thereon forobtaining a resource for accessing a target cell in the network; and aprocessor, operably coupled to the non-transitory memory, configured toexecute the instructions of: receiving a handover command including alist of physical random access channel (PRACH) resources associated witha plurality of Synchronization Signal Blocks (SSB)s or Channel StateInformation Reference Signals (CSI-RS)s of the target cell, and athreshold for determining whether the PRACH resources associated withthe SSBs or CSI-RSs be used for performing random access; detecting theSSBs or CSI-RSs associated with the target cell; determining one or morethe detected SSBs or CSI-RSs meets an SSB and/or CSI-RS threshold forperforming random access; selecting one of the determined SSBs orCSI-RSs; selecting one of the PRACH resources associated with the oneselected determined SSB or CSI-RS; and transmitting a PRACH preambleusing the one selected PRACH resource.
 2. The apparatus of claim 1,wherein the list of PRACH resources corresponds to dedicated PRACHresources, common PRACH resources or combinations thereof.
 3. Theapparatus of claim 2, wherein the selecting one of the determined SSBsor CSI-RSs instruction further includes prioritizing the SSBs or CSI-RSswith dedicated PRACH resources.
 4. The apparatus of claim 1, wherein thehandover command is received in a radio resource control (RRC)signaling.
 5. The apparatus of claim 1, wherein the apparatus determinesnone of the detected SSBs or CSI-RSs meets a threshold for performingrandom access; and selects a best one of the SSBs among the pluraldetected SSBs.
 6. The apparatus of claim 1, wherein the PRACH resourcecorresponds to the next PRACH occasion.
 7. The apparatus of claim 1,wherein the selecting a PRACH resource instruction further includesselecting a preamble associated with the one selected-determined SSB orCSI-RS.
 8. The apparatus of claim 7, wherein the preamble is randomlyselected with equal probability from the preambles associated with theone selected determined SSB or CSI-RS.
 9. The apparatus of claim 1,wherein the received handover command includes a threshold fordetermining if the PRACH resources associated with the one selecteddetermined SSB can be used for performing random access.
 10. Theapparatus of claim 1, wherein the received handover command includes athreshold for determining if the PRACH resources associated with the oneselected determined CSI-RS can be used for performing random access. 11.The apparatus of claim 1, wherein the threshold received in the handovercommand is a reference signal received power (RSRP)-based threshold. 12.The apparatus of claim 5, wherein the best SSB beam is determined as thedetected SSB with the highest RSRP value.
 13. The apparatus of claim 1,wherein the apparatus is a user equipment.
 14. An apparatus in a networkcomprising: a non-transitory memory including instructions storedthereon for obtaining a resource for accessing a target cell in thenetwork; and a processor, operably coupled to the non-transitory memory,configured to execute the instructions of: transmitting, to a userequipment (UE), a handover command including a list of physical randomaccess channel (PRACH) resources associated with a plurality ofSynchronization Signal Blocks (SSB)s or Channel State InformationReference Signals (CSI-RS)s of a target cell, and a threshold fordetermining whether the PRACH resources associated with the SSBs orCSI-RSs can be used for performing random access; determining the UE hasaccessed the target cell; and transmitting, to the target cell, bufferedand in-transit data associated with the UE.
 15. The apparatus of claim14, wherein the list of PRACH resources corresponds to dedicated PRACHresources, common PRACH resources or combinations thereof, and thehandover command is sent in a radio resource control (RRC) signaling.16. A method comprising: transmitting, to a user equipment (UE) in anetwork, a handover command including a list of physical random accesschannel (PRACH) resources associated with a plurality of SynchronizationSignal Blocks (SSB)s or Channel State Information Reference Signals(CSI-RS)s of a target cell, and a threshold for determining whether aPRACH resource associated with the SSBs or a CSI-RSs of the target cellcan be used for performing random access; determining the UE hasaccessed the target cell; and transmitting, to the target cell, bufferedand in-transit data associated with the UE.
 17. The method of claim 16,wherein the transmitting and determining steps are performed by a basestation.
 18. The method of claim 16, wherein the list of PRACH resourcescorresponds to dedicated PRACH resources, common PRACH resources orcombinations thereof, and the handover command is sent in a radioresource control (RRC) signaling.
 19. The apparatus of claim 2, whereinthe selection of one of the determined SSBs or CSI-RSs instructionincludes prioritizing the SSBs or CSI-RSs with common PRACH resources.20. The apparatus of claim 14, wherein the apparatus is a base station.